diff --git a/Cargo.lock b/Cargo.lock
index b38f438ba4..df79bf294f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1430,6 +1430,15 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "06d198e9919d9822d5f7083ba8530e04de87841eaf21ead9af8f2304efd57c89"
 
+[[package]]
+name = "is_executable"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fa9acdc6d67b75e626ad644734e8bc6df893d9cd2a834129065d3dd6158ea9c8"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "itertools"
 version = "0.10.3"
@@ -1890,6 +1899,7 @@ dependencies = [
 name = "nu-cli"
 version = "0.1.0"
 dependencies = [
+ "is_executable",
  "log",
  "miette",
  "nu-ansi-term",
@@ -1937,6 +1947,7 @@ dependencies = [
  "indexmap",
  "itertools",
  "lazy_static",
+ "log",
  "lscolors",
  "md-5",
  "meval",
@@ -1980,6 +1991,7 @@ dependencies = [
  "url",
  "users",
  "uuid",
+ "which",
  "zip",
 ]
 
diff --git a/Cargo.toml b/Cargo.toml
index 6c4862c27e..3d62988315 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -63,6 +63,7 @@ default = [
 	"plugin",
 	"inc",
 	"example",
+	"which"
 	]
 
 stable = ["default"]
@@ -80,6 +81,8 @@ wasi = ["inc"]
 inc = ["nu_plugin_inc"]
 example = ["nu_plugin_example"]
 
+which = ["nu-command/which"]
+
 # Extra
 gstat = ["nu_plugin_gstat"]
 
diff --git a/crates/nu-cli/Cargo.toml b/crates/nu-cli/Cargo.toml
index 38361ac94f..44496983e1 100644
--- a/crates/nu-cli/Cargo.toml
+++ b/crates/nu-cli/Cargo.toml
@@ -16,3 +16,4 @@ miette = { version = "3.0.0", features = ["fancy"] }
 thiserror = "1.0.29"
 reedline = { git = "https://github.com/nushell/reedline", branch = "main" }
 log = "0.4"
+is_executable = "1.0.1"
\ No newline at end of file
diff --git a/crates/nu-cli/src/completions.rs b/crates/nu-cli/src/completions.rs
index 028dd93328..38bf7ccaa6 100644
--- a/crates/nu-cli/src/completions.rs
+++ b/crates/nu-cli/src/completions.rs
@@ -19,6 +19,170 @@ impl NuCompleter {
         Self { engine_state }
     }
 
+    fn external_command_completion(&self, prefix: &str) -> Vec<String> {
+        let mut executables = vec![];
+
+        let paths;
+
+        #[cfg(windows)]
+        {
+            paths = self.engine_state.env_vars.get("Path");
+        }
+
+        #[cfg(not(windows))]
+        {
+            paths = self.engine_state.env_vars.get("PATH");
+        }
+
+        if let Some(paths) = paths {
+            if let Ok(paths) = paths.as_list() {
+                for path in paths {
+                    let path = path.as_string().unwrap_or_default();
+
+                    if let Ok(mut contents) = std::fs::read_dir(path) {
+                        while let Some(Ok(item)) = contents.next() {
+                            if !executables.contains(
+                                &item
+                                    .path()
+                                    .file_name()
+                                    .map(|x| x.to_string_lossy().to_string())
+                                    .unwrap_or_default(),
+                            ) && matches!(
+                                item.path()
+                                    .file_name()
+                                    .map(|x| x.to_string_lossy().starts_with(prefix)),
+                                Some(true)
+                            ) && is_executable::is_executable(&item.path())
+                            {
+                                if let Ok(name) = item.file_name().into_string() {
+                                    executables.push(name);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        executables
+    }
+
+    fn complete_variables(
+        &self,
+        working_set: &StateWorkingSet,
+        prefix: &[u8],
+        span: Span,
+        offset: usize,
+    ) -> Vec<(reedline::Span, String)> {
+        let mut output = vec![];
+
+        let builtins = ["$nu", "$scope", "$in", "$config", "$env"];
+
+        for builtin in builtins {
+            if builtin.as_bytes().starts_with(prefix) {
+                output.push((
+                    reedline::Span {
+                        start: span.start - offset,
+                        end: span.end - offset,
+                    },
+                    builtin.to_string(),
+                ));
+            }
+        }
+
+        for scope in &working_set.delta.scope {
+            for v in &scope.vars {
+                if v.0.starts_with(prefix) {
+                    output.push((
+                        reedline::Span {
+                            start: span.start - offset,
+                            end: span.end - offset,
+                        },
+                        String::from_utf8_lossy(v.0).to_string(),
+                    ));
+                }
+            }
+        }
+        for scope in &self.engine_state.scope {
+            for v in &scope.vars {
+                if v.0.starts_with(prefix) {
+                    output.push((
+                        reedline::Span {
+                            start: span.start - offset,
+                            end: span.end - offset,
+                        },
+                        String::from_utf8_lossy(v.0).to_string(),
+                    ));
+                }
+            }
+        }
+
+        output.dedup();
+
+        output
+    }
+
+    fn complete_filepath_and_commands(
+        &self,
+        working_set: &StateWorkingSet,
+        span: Span,
+        offset: usize,
+    ) -> Vec<(reedline::Span, String)> {
+        let prefix = working_set.get_span_contents(span);
+
+        let results = working_set
+            .find_commands_by_prefix(prefix)
+            .into_iter()
+            .map(move |x| {
+                (
+                    reedline::Span {
+                        start: span.start - offset,
+                        end: span.end - offset,
+                    },
+                    String::from_utf8_lossy(&x).to_string(),
+                )
+            });
+        let cwd = if let Some(d) = self.engine_state.env_vars.get("PWD") {
+            match d.as_string() {
+                Ok(s) => s,
+                Err(_) => "".to_string(),
+            }
+        } else {
+            "".to_string()
+        };
+
+        let prefix = String::from_utf8_lossy(prefix).to_string();
+        let results_paths = file_path_completion(span, &prefix, &cwd)
+            .into_iter()
+            .map(move |x| {
+                (
+                    reedline::Span {
+                        start: x.0.start - offset,
+                        end: x.0.end - offset,
+                    },
+                    x.1,
+                )
+            });
+
+        let results_external =
+            self.external_command_completion(&prefix)
+                .into_iter()
+                .map(move |x| {
+                    (
+                        reedline::Span {
+                            start: span.start - offset,
+                            end: span.end - offset,
+                        },
+                        x,
+                    )
+                });
+
+        results
+            .chain(results_paths.into_iter())
+            .chain(results_external.into_iter())
+            .collect()
+    }
+
     fn completion_helper(&self, line: &str, pos: usize) -> Vec<(reedline::Span, String)> {
         let mut working_set = StateWorkingSet::new(&self.engine_state);
         let offset = working_set.next_span_start();
@@ -28,35 +192,20 @@ impl NuCompleter {
         for stmt in output.stmts.into_iter() {
             if let Statement::Pipeline(pipeline) = stmt {
                 for expr in pipeline.expressions {
-                    if pos >= expr.span.start
-                        && (pos <= (line.len() + offset) || pos <= expr.span.end)
-                    {
-                        let possible_cmd = working_set.get_span_contents(Span {
-                            start: expr.span.start,
-                            end: pos,
-                        });
-
-                        let results = working_set.find_commands_by_prefix(possible_cmd);
-
-                        if !results.is_empty() {
-                            return results
-                                .into_iter()
-                                .map(move |x| {
-                                    (
-                                        reedline::Span {
-                                            start: expr.span.start - offset,
-                                            end: pos - offset,
-                                        },
-                                        String::from_utf8_lossy(&x).to_string(),
-                                    )
-                                })
-                                .collect();
-                        }
-                    }
-
                     let flattened = flatten_expression(&working_set, &expr);
                     for flat in flattened {
                         if pos >= flat.0.start && pos <= flat.0.end {
+                            let prefix = working_set.get_span_contents(flat.0);
+
+                            if prefix.starts_with(b"$") {
+                                return self.complete_variables(
+                                    &working_set,
+                                    prefix,
+                                    flat.0,
+                                    offset,
+                                );
+                            }
+
                             match &flat.1 {
                                 nu_parser::FlatShape::Custom(custom_completion) => {
                                     let prefix = working_set.get_span_contents(flat.0).to_vec();
@@ -81,8 +230,8 @@ impl NuCompleter {
                                             .into_iter()
                                             .map(move |x| {
                                                 let s = x.as_string().expect(
-                                        "FIXME: better error handling for custom completions",
-                                    );
+                                                    "FIXME: better error handling for custom completions",
+                                                );
 
                                                 (
                                                     reedline::Span {
@@ -102,44 +251,11 @@ impl NuCompleter {
                                 nu_parser::FlatShape::External
                                 | nu_parser::FlatShape::InternalCall
                                 | nu_parser::FlatShape::String => {
-                                    let prefix = working_set.get_span_contents(flat.0);
-                                    let results = working_set.find_commands_by_prefix(prefix);
-                                    let cwd = if let Some(d) = self.engine_state.env_vars.get("PWD")
-                                    {
-                                        match d.as_string() {
-                                            Ok(s) => s,
-                                            Err(_) => "".to_string(),
-                                        }
-                                    } else {
-                                        "".to_string()
-                                    };
-
-                                    let prefix = String::from_utf8_lossy(prefix).to_string();
-                                    let results2 = file_path_completion(flat.0, &prefix, &cwd)
-                                        .into_iter()
-                                        .map(move |x| {
-                                            (
-                                                reedline::Span {
-                                                    start: x.0.start - offset,
-                                                    end: x.0.end - offset,
-                                                },
-                                                x.1,
-                                            )
-                                        });
-
-                                    return results
-                                        .into_iter()
-                                        .map(move |x| {
-                                            (
-                                                reedline::Span {
-                                                    start: flat.0.start - offset,
-                                                    end: flat.0.end - offset,
-                                                },
-                                                String::from_utf8_lossy(&x).to_string(),
-                                            )
-                                        })
-                                        .chain(results2.into_iter())
-                                        .collect();
+                                    return self.complete_filepath_and_commands(
+                                        &working_set,
+                                        flat.0,
+                                        offset,
+                                    );
                                 }
                                 nu_parser::FlatShape::Filepath
                                 | nu_parser::FlatShape::GlobPattern
@@ -171,41 +287,7 @@ impl NuCompleter {
                                         })
                                         .collect();
                                 }
-                                _ => {
-                                    let prefix = working_set.get_span_contents(flat.0);
-
-                                    if prefix.starts_with(b"$") {
-                                        let mut output = vec![];
-
-                                        for scope in &working_set.delta.scope {
-                                            for v in &scope.vars {
-                                                if v.0.starts_with(prefix) {
-                                                    output.push((
-                                                        reedline::Span {
-                                                            start: flat.0.start - offset,
-                                                            end: flat.0.end - offset,
-                                                        },
-                                                        String::from_utf8_lossy(v.0).to_string(),
-                                                    ));
-                                                }
-                                            }
-                                        }
-                                        for scope in &self.engine_state.scope {
-                                            for v in &scope.vars {
-                                                if v.0.starts_with(prefix) {
-                                                    output.push((
-                                                        reedline::Span {
-                                                            start: flat.0.start - offset,
-                                                            end: flat.0.end - offset,
-                                                        },
-                                                        String::from_utf8_lossy(v.0).to_string(),
-                                                    ));
-                                                }
-                                            }
-                                        }
-                                        return output;
-                                    }
-                                }
+                                _ => {}
                             }
                         }
                     }
diff --git a/crates/nu-command/Cargo.toml b/crates/nu-command/Cargo.toml
index 2baeba13ad..c81b5f9556 100644
--- a/crates/nu-command/Cargo.toml
+++ b/crates/nu-command/Cargo.toml
@@ -72,6 +72,8 @@ encoding_rs = "0.8.30"
 num = { version = "0.4.0", optional = true }
 reqwest = {version = "0.11", features = ["blocking"] }
 mime = "0.3.16"
+log = "0.4.14"
+which = { version = "4.2.2", optional = true }
 
 [target.'cfg(unix)'.dependencies]
 umask = "1.0.0"
diff --git a/crates/nu-command/src/default_context.rs b/crates/nu-command/src/default_context.rs
index f6b8617e9c..6a925eee54 100644
--- a/crates/nu-command/src/default_context.rs
+++ b/crates/nu-command/src/default_context.rs
@@ -112,6 +112,9 @@ pub fn create_default_context(cwd: impl AsRef<Path>) -> EngineState {
             Sys,
         };
 
+        #[cfg(feature = "which")]
+        bind_command! { Which };
+
         // Strings
         bind_command! {
             BuildString,
diff --git a/crates/nu-command/src/system/mod.rs b/crates/nu-command/src/system/mod.rs
index a921225973..3225ddde7b 100644
--- a/crates/nu-command/src/system/mod.rs
+++ b/crates/nu-command/src/system/mod.rs
@@ -2,8 +2,10 @@ mod benchmark;
 mod ps;
 mod run_external;
 mod sys;
+mod which_;
 
 pub use benchmark::Benchmark;
 pub use ps::Ps;
 pub use run_external::{External, ExternalCommand};
 pub use sys::Sys;
+pub use which_::Which;
diff --git a/crates/nu-command/src/system/which_.rs b/crates/nu-command/src/system/which_.rs
new file mode 100644
index 0000000000..529a38f1d3
--- /dev/null
+++ b/crates/nu-command/src/system/which_.rs
@@ -0,0 +1,256 @@
+use itertools::Itertools;
+use log::trace;
+use nu_engine::CallExt;
+use nu_protocol::{
+    ast::Call,
+    engine::{Command, EngineState, Stack},
+    Category, Example, IntoInterruptiblePipelineData, PipelineData, ShellError, Signature, Span,
+    Spanned, SyntaxShape, Value,
+};
+
+#[derive(Clone)]
+pub struct Which;
+
+impl Command for Which {
+    fn name(&self) -> &str {
+        "which"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("which")
+            .required("application", SyntaxShape::String, "application")
+            .rest("rest", SyntaxShape::String, "additional applications")
+            .switch("all", "list all executables", Some('a'))
+            .category(Category::System)
+    }
+
+    fn usage(&self) -> &str {
+        "Finds a program file, alias or custom command."
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        _input: PipelineData,
+    ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
+        which(engine_state, stack, call)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Find if the 'myapp' application is available",
+            example: "which myapp",
+            result: None,
+        }]
+    }
+}
+
+/// Shortcuts for creating an entry to the output table
+fn entry(arg: impl Into<String>, path: Value, builtin: bool, span: Span) -> Value {
+    let mut cols = vec![];
+    let mut vals = vec![];
+
+    cols.push("arg".to_string());
+    vals.push(Value::string(arg.into(), span));
+
+    cols.push("path".to_string());
+    vals.push(path);
+
+    cols.push("builtin".to_string());
+    vals.push(Value::Bool { val: builtin, span });
+
+    Value::Record { cols, vals, span }
+}
+
+macro_rules! create_entry {
+    ($arg:expr, $path:expr, $span:expr, $is_builtin:expr) => {
+        entry(
+            $arg.clone(),
+            Value::string($path.to_string(), $span),
+            $is_builtin,
+            $span,
+        )
+    };
+}
+
+fn get_entries_in_aliases(engine_state: &EngineState, name: &str, span: Span) -> Vec<Value> {
+    let aliases = engine_state.find_aliases(name);
+
+    let aliases = aliases
+        .into_iter()
+        .map(|spans| {
+            spans
+                .into_iter()
+                .map(|span| {
+                    String::from_utf8_lossy(engine_state.get_span_contents(&span)).to_string()
+                })
+                .join(" ")
+        })
+        .map(|alias| create_entry!(name, format!("Nushell alias: {}", alias), span, false))
+        .collect::<Vec<_>>();
+    trace!("Found {} aliases", aliases.len());
+    aliases
+}
+
+fn get_entries_in_custom_command(engine_state: &EngineState, name: &str, span: Span) -> Vec<Value> {
+    let custom_commands = engine_state.find_custom_commands(name);
+
+    custom_commands
+        .into_iter()
+        .map(|_| create_entry!(name, "Nushell custom command", span, false))
+        .collect::<Vec<_>>()
+}
+
+fn get_entry_in_commands(engine_state: &EngineState, name: &str, span: Span) -> Option<Value> {
+    if engine_state.find_decl(name.as_bytes()).is_some() {
+        Some(create_entry!(name, "Nushell built-in command", span, true))
+    } else {
+        None
+    }
+}
+
+fn get_entries_in_nu(
+    engine_state: &EngineState,
+    name: &str,
+    span: Span,
+    skip_after_first_found: bool,
+) -> Vec<Value> {
+    let mut all_entries = vec![];
+
+    all_entries.extend(get_entries_in_aliases(engine_state, name, span));
+    if !all_entries.is_empty() && skip_after_first_found {
+        return all_entries;
+    }
+
+    all_entries.extend(get_entries_in_custom_command(engine_state, name, span));
+    if !all_entries.is_empty() && skip_after_first_found {
+        return all_entries;
+    }
+
+    if let Some(entry) = get_entry_in_commands(engine_state, name, span) {
+        all_entries.push(entry);
+    }
+
+    all_entries
+}
+
+#[allow(unused)]
+macro_rules! entry_path {
+    ($arg:expr, $path:expr, $span:expr) => {
+        entry($arg.clone(), Value::string($path, $span), false, $span)
+    };
+}
+
+#[cfg(feature = "which")]
+fn get_first_entry_in_path(item: &str, span: Span) -> Option<Value> {
+    which::which(item)
+        .map(|path| entry_path!(item, path.to_string_lossy().to_string(), span))
+        .ok()
+}
+
+#[cfg(not(feature = "which"))]
+fn get_first_entry_in_path(_: &str, _: Span) -> Option<Value> {
+    None
+}
+
+#[cfg(feature = "which")]
+fn get_all_entries_in_path(item: &str, span: Span) -> Vec<Value> {
+    which::which_all(&item)
+        .map(|iter| {
+            iter.map(|path| entry_path!(item, path.to_string_lossy().to_string(), span))
+                .collect()
+        })
+        .unwrap_or_default()
+}
+#[cfg(not(feature = "which"))]
+fn get_all_entries_in_path(_: &str, _: Span) -> Vec<Value> {
+    vec![]
+}
+
+#[derive(Debug)]
+struct WhichArgs {
+    applications: Vec<Spanned<String>>,
+    all: bool,
+}
+
+fn which_single(application: Spanned<String>, all: bool, engine_state: &EngineState) -> Vec<Value> {
+    let (external, prog_name) = if application.item.starts_with('^') {
+        (true, application.item[1..].to_string())
+    } else {
+        (false, application.item.clone())
+    };
+
+    //If prog_name is an external command, don't search for nu-specific programs
+    //If all is false, we can save some time by only searching for the first matching
+    //program
+    //This match handles all different cases
+    match (all, external) {
+        (true, true) => get_all_entries_in_path(&prog_name, application.span),
+        (true, false) => {
+            let mut output: Vec<Value> = vec![];
+            output.extend(get_entries_in_nu(
+                engine_state,
+                &prog_name,
+                application.span,
+                false,
+            ));
+            output.extend(get_all_entries_in_path(&prog_name, application.span));
+            output
+        }
+        (false, true) => {
+            if let Some(entry) = get_first_entry_in_path(&prog_name, application.span) {
+                return vec![entry];
+            }
+            vec![]
+        }
+        (false, false) => {
+            let nu_entries = get_entries_in_nu(engine_state, &prog_name, application.span, true);
+            if !nu_entries.is_empty() {
+                return vec![nu_entries[0].clone()];
+            } else if let Some(entry) = get_first_entry_in_path(&prog_name, application.span) {
+                return vec![entry];
+            }
+            vec![]
+        }
+    }
+}
+
+fn which(
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+) -> Result<PipelineData, ShellError> {
+    let which_args = WhichArgs {
+        applications: call.rest(engine_state, stack, 0)?,
+        all: call.has_flag("all"),
+    };
+    let ctrlc = engine_state.ctrlc.clone();
+
+    if which_args.applications.is_empty() {
+        return Err(ShellError::MissingParameter(
+            "application".into(),
+            call.head,
+        ));
+    }
+
+    let mut output = vec![];
+
+    for app in which_args.applications {
+        let values = which_single(app, which_args.all, engine_state);
+        output.extend(values);
+    }
+
+    Ok(output.into_iter().into_pipeline_data(ctrlc))
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        crate::test_examples(Which)
+    }
+}
diff --git a/crates/nu-protocol/src/engine/engine_state.rs b/crates/nu-protocol/src/engine/engine_state.rs
index 26f2adae99..7377feaa41 100644
--- a/crates/nu-protocol/src/engine/engine_state.rs
+++ b/crates/nu-protocol/src/engine/engine_state.rs
@@ -344,6 +344,34 @@ impl EngineState {
         }
     }
 
+    pub fn find_aliases(&self, name: &str) -> Vec<Vec<Span>> {
+        let mut output = vec![];
+
+        for frame in &self.scope {
+            if let Some(alias) = frame.aliases.get(name.as_bytes()) {
+                output.push(alias.clone());
+            }
+        }
+
+        output
+    }
+
+    pub fn find_custom_commands(&self, name: &str) -> Vec<Block> {
+        let mut output = vec![];
+
+        for frame in &self.scope {
+            if let Some(decl_id) = frame.decls.get(name.as_bytes()) {
+                let decl = self.get_decl(*decl_id);
+
+                if let Some(block_id) = decl.get_block_id() {
+                    output.push(self.get_block(block_id).clone());
+                }
+            }
+        }
+
+        output
+    }
+
     pub fn find_decl(&self, name: &[u8]) -> Option<DeclId> {
         let mut visibility: Visibility = Visibility::new();