diff --git a/README.md b/README.md
index 1437413..0270c72 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,7 @@ github-code-search query "TODO" --org my-org
 ```
 
 > [!TIP]
+> `GITHUB_TOKEN` falls back to `gh auth token` when unset and the [GitHub CLI](https://cli.github.com/) is installed and authenticated.
 > Set `GCS_DEFAULT_ORG=my-org` to omit `--org` on every call. See [Environment variables](https://fulll.github.io/github-code-search/reference/environment).
 
 ## Features
diff --git a/docs/getting-started/first-search.md b/docs/getting-started/first-search.md
index 49e35c9..f5032f8 100644
--- a/docs/getting-started/first-search.md
+++ b/docs/getting-started/first-search.md
@@ -7,7 +7,7 @@ This guide walks through a complete search session from first invocation to stru
 Make sure you have:
 
 - `github-code-search` [installed](/getting-started/installation)
-- `GITHUB_TOKEN` set in your environment ([see Prerequisites](/getting-started/))
+- `GITHUB_TOKEN` set in your environment, or the [GitHub CLI](https://cli.github.com/) installed and authenticated ([see Prerequisites](/getting-started/))
 
 ## Run a search
 
diff --git a/docs/getting-started/index.md b/docs/getting-started/index.md
index 42be454..bf6667a 100644
--- a/docs/getting-started/index.md
+++ b/docs/getting-started/index.md
@@ -1,6 +1,6 @@
 # Prerequisites
 
-The only runtime prerequisite is a **GitHub personal access token**. The pre-compiled binary is self-contained and has no runtime dependency — you do not need Bun to run it.
+The only runtime prerequisite is a **GitHub personal access token** (or the [GitHub CLI](https://cli.github.com/), see below). The pre-compiled binary is self-contained and has no runtime dependency — you do not need Bun to run it.
 
 ::: tip Building from source?
 If you want to build `github-code-search` from source, you will additionally need [Bun](https://bun.sh) ≥ 1.0. See the [Installation guide](/getting-started/installation#from-source).
@@ -35,6 +35,10 @@ Add this to your shell profile (`~/.zshrc`, `~/.bashrc`, `~/.config/fish/config.
 Never commit your token to version control. Use environment variables or a secrets manager.
 :::
 
+::: tip Already using the GitHub CLI?
+If `GITHUB_TOKEN` isn't set and [`gh`](https://cli.github.com/) is installed and authenticated (`gh auth login`), `github-code-search` automatically retrieves a token via `gh auth token` — no extra setup needed. Applies to the search commands and the `upgrade` subcommand.
+:::
+
 ## Default organization
 
 If you mostly search a single organization, set `GCS_DEFAULT_ORG` once to omit `--org` on every call:
diff --git a/docs/reference/environment.md b/docs/reference/environment.md
index 1125d45..67a65b2 100644
--- a/docs/reference/environment.md
+++ b/docs/reference/environment.md
@@ -6,11 +6,13 @@
 
 | Variable                       | Required | Default              | Description                                                                                                                                                        |
 | ------------------------------ | -------- | -------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
-| `GITHUB_TOKEN`                 | ✅       | —                    | GitHub personal access token. Used to authenticate API calls. See [Prerequisites](/getting-started/).                                                              |
+| `GITHUB_TOKEN`                 | ✅¹      | —                    | GitHub personal access token. Used to authenticate API calls. See [Prerequisites](/getting-started/).                                                              |
 | `GCS_DEFAULT_ORG`              | ❌       | —                    | Default value for `--org` when the flag is omitted. An explicit `--org` always takes precedence. See [CLI options](/reference/cli-options).                        |
 | `CI`                           | ❌       | `false`              | Set to `true` to disable the interactive TUI and print results directly to stdout. Automatically set by GitHub Actions, GitLab CI, CircleCI and most CI platforms. |
 | `GITHUB_CODE_SEARCH_CACHE_DIR` | ❌       | OS-dependent (below) | Override the directory used to cache the team list when `--group-by-team-prefix` is set.                                                                           |
 
+¹ Required for the search commands, unless the [GitHub CLI](https://cli.github.com/) is installed and authenticated — `gh auth token` is used as a fallback. The `upgrade` subcommand never requires a token; it only uses one opportunistically (higher GitHub API rate limits) when available.
+
 ## `GITHUB_TOKEN`
 
 ```bash
@@ -25,6 +27,10 @@ Add this to your shell profile (`~/.zshrc`, `~/.bashrc`, `~/.config/fish/config.
 | `public_repo` | Searching public repositories only                     |
 | `read:org`    | Using [`--group-by-team-prefix`](/usage/team-grouping) |
 
+::: tip Already using the GitHub CLI?
+If `GITHUB_TOKEN` isn't set and [`gh`](https://cli.github.com/) is installed and authenticated (`gh auth login`), `github-code-search` automatically retrieves a token via `gh auth token` — no extra setup needed. Applies to the search commands and the `upgrade` subcommand.
+:::
+
 ## `GCS_DEFAULT_ORG`
 
 ```bash
diff --git a/docs/usage/upgrade.md b/docs/usage/upgrade.md
index b2b8cbd..a372d72 100644
--- a/docs/usage/upgrade.md
+++ b/docs/usage/upgrade.md
@@ -30,7 +30,7 @@ Successfully upgraded to v1.3.0.
 
 ## Token requirement
 
-The `upgrade` subcommand works without a `GITHUB_TOKEN`. A token is used only if the `GITHUB_TOKEN` environment variable is already set (to avoid GitHub API rate limiting on the release fetch).
+The `upgrade` subcommand works without a `GITHUB_TOKEN`. A token is used only if the `GITHUB_TOKEN` environment variable is set, or otherwise retrieved via `gh auth token` when the [GitHub CLI](https://cli.github.com/) is installed and authenticated (to avoid GitHub API rate limiting on the release fetch).
 
 ## Checking the current version
 
diff --git a/github-code-search.ts b/github-code-search.ts
index bfbb69d..a6f583a 100644
--- a/github-code-search.ts
+++ b/github-code-search.ts
@@ -9,7 +9,8 @@
  *   github-code-search query <query> --org <org> [options]
  *
  * Requirements:
- *   GITHUB_TOKEN env var must be set (for search; optional for upgrade).
+ *   GITHUB_TOKEN env var must be set (for search; optional for upgrade),
+ *   or the GitHub CLI (`gh`) installed and authenticated as a fallback.
  */
 
 import { Command, Option, program } from "commander";
@@ -33,6 +34,7 @@ import {
 import { checkForUpdate } from "./src/upgrade.ts";
 import { runInteractive } from "./src/tui.ts";
 import { generateCompletion, detectShell } from "./src/completions.ts";
+import { getGhAuthToken } from "./src/gh-cli.ts";
 import {
   buildApiQuery,
   detectPathWildcardLimitation,
@@ -281,9 +283,17 @@ async function searchAction(
   },
 ): Promise<void> {
   // ─── GitHub API token ───────────────────────────────────────────────────────
-  const GITHUB_TOKEN = process.env.GITHUB_TOKEN;
+  // Falls back to `gh auth token` when GITHUB_TOKEN isn't set and the GitHub
+  // CLI is installed and authenticated — see src/gh-cli.ts.
+  const GITHUB_TOKEN = process.env.GITHUB_TOKEN ?? getGhAuthToken();
   if (!GITHUB_TOKEN) {
     console.error(style.red("Error: GITHUB_TOKEN environment variable is not set."));
+    console.error(
+      style.dim(
+        "Tip: install and authenticate the GitHub CLI (`gh auth login`) to use " +
+          "`gh auth token` as a fallback.",
+      ),
+    );
     process.exit(1);
   }
 
@@ -590,7 +600,8 @@ program
   .option("--debug", "Print debug information for troubleshooting")
   .action(async (opts: { debug?: boolean }) => {
     const { performUpgrade } = await import("./src/upgrade.ts");
-    const token = process.env.GITHUB_TOKEN;
+    // Falls back to `gh auth token` — same as the search commands, see src/gh-cli.ts.
+    const token = process.env.GITHUB_TOKEN ?? getGhAuthToken();
     // Fix: in some Bun versions, process.execPath returns the Bun runtime path
     // (e.g. ~/.bun/bin/bun) or an internal /$bunfs/ path instead of the compiled
     // binary path — which causes the mv to fail or replace the wrong file.
diff --git a/src/gh-cli.test.ts b/src/gh-cli.test.ts
new file mode 100644
index 0000000..70a04d1
--- /dev/null
+++ b/src/gh-cli.test.ts
@@ -0,0 +1,83 @@
+import { afterEach, describe, expect, it } from "bun:test";
+import { getGhAuthToken, resolveGhAuthToken } from "./gh-cli.ts";
+
+const ghIsAvailable = () => true;
+const ghAuthTokenSucceeds = () => ({ exitCode: 0, stdout: "token-value" });
+
+describe("resolveGhAuthToken", () => {
+  it("returns undefined when gh is not installed", () => {
+    const result = resolveGhAuthToken(
+      () => false,
+      () => {
+        throw new Error("runAuthToken must not be called when gh isn't installed");
+      },
+    );
+    expect(result).toBeUndefined();
+  });
+
+  it("returns the trimmed token when gh auth token succeeds", () => {
+    const result = resolveGhAuthToken(
+      () => true,
+      () => ({ exitCode: 0, stdout: "ghp_abc123\n" }),
+    );
+    expect(result).toBe("ghp_abc123");
+  });
+
+  it("returns undefined when gh auth token exits with a non-zero code", () => {
+    const result = resolveGhAuthToken(
+      () => true,
+      () => ({ exitCode: 1, stdout: "" }),
+    );
+    expect(result).toBeUndefined();
+  });
+
+  it("returns undefined when gh auth token succeeds but prints only whitespace", () => {
+    const result = resolveGhAuthToken(
+      () => true,
+      () => ({ exitCode: 0, stdout: "   \n" }),
+    );
+    expect(result).toBeUndefined();
+  });
+
+  it("is pure — calling it twice with the same inputs yields the same result", () => {
+    const first = resolveGhAuthToken(ghIsAvailable, ghAuthTokenSucceeds);
+    const second = resolveGhAuthToken(ghIsAvailable, ghAuthTokenSucceeds);
+    expect(first).toBe(second);
+  });
+});
+
+describe("getGhAuthToken", () => {
+  const originalWhich = Bun.which;
+  const originalSpawnSync = Bun.spawnSync;
+
+  afterEach(() => {
+    Bun.which = originalWhich;
+    Bun.spawnSync = originalSpawnSync;
+  });
+
+  it("returns undefined when gh is not on PATH (Bun.spawnSync never called)", () => {
+    Bun.which = (() => null) as typeof Bun.which;
+    Bun.spawnSync = (() => {
+      throw new Error("spawnSync must not be called when gh isn't on PATH");
+    }) as unknown as typeof Bun.spawnSync;
+    expect(getGhAuthToken()).toBeUndefined();
+  });
+
+  it("returns the trimmed token when gh is on PATH and gh auth token succeeds", () => {
+    Bun.which = (() => "/usr/local/bin/gh") as typeof Bun.which;
+    Bun.spawnSync = ((..._args: unknown[]) => ({
+      exitCode: 0,
+      stdout: Buffer.from("ghp_real123\n"),
+    })) as unknown as typeof Bun.spawnSync;
+    expect(getGhAuthToken()).toBe("ghp_real123");
+  });
+
+  it("returns undefined when gh auth token exits non-zero (not authenticated)", () => {
+    Bun.which = (() => "/usr/local/bin/gh") as typeof Bun.which;
+    Bun.spawnSync = ((..._args: unknown[]) => ({
+      exitCode: 1,
+      stdout: Buffer.from(""),
+    })) as unknown as typeof Bun.spawnSync;
+    expect(getGhAuthToken()).toBeUndefined();
+  });
+});
diff --git a/src/gh-cli.ts b/src/gh-cli.ts
new file mode 100644
index 0000000..82ee084
--- /dev/null
+++ b/src/gh-cli.ts
@@ -0,0 +1,46 @@
+// ─── gh CLI token fallback ─────────────────────────────────────────────────────
+//
+// Fallback for GITHUB_TOKEN: when the env var isn't set, detect whether the
+// GitHub CLI (`gh`) is installed and, if so, retrieve a token via
+// `gh auth token`. Pure decision logic lives in `resolveGhAuthToken` (unit
+// tested via injected `which`/`runAuthToken`); `getGhAuthToken` is the sole
+// call site for the real `Bun.which` / subprocess spawn, tested by
+// reassigning those globals rather than spawning a real `gh` process.
+
+/** Result of a single subprocess invocation, abstracted for testability. */
+export interface ExecResult {
+  exitCode: number;
+  stdout: string;
+}
+
+/**
+ * Returns the token from `gh auth token` when `gh` is installed and the
+ * command succeeds with non-empty output, `undefined` otherwise (not
+ * installed, non-zero exit code, or blank output). Pure — `which` and
+ * `runAuthToken` are injected so this can be unit tested without spawning a
+ * real subprocess.
+ */
+export function resolveGhAuthToken(
+  which: (cmd: string) => boolean,
+  runAuthToken: () => ExecResult,
+): string | undefined {
+  if (!which("gh")) return undefined;
+  const result = runAuthToken();
+  if (result.exitCode !== 0) return undefined;
+  const token = result.stdout.trim();
+  return token.length > 0 ? token : undefined;
+}
+
+/**
+ * Real Bun call site: checks for `gh` on PATH and, if present, runs
+ * `gh auth token` synchronously to retrieve a token.
+ */
+export function getGhAuthToken(): string | undefined {
+  return resolveGhAuthToken(
+    (cmd) => Bun.which(cmd) !== null,
+    () => {
+      const proc = Bun.spawnSync(["gh", "auth", "token"]);
+      return { exitCode: proc.exitCode, stdout: proc.stdout.toString() };
+    },
+  );
+}