diff --git a/CHANGELOG.md b/CHANGELOG.md
index d2170c400940..2cd3ea0ad8eb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Suggest container query variants ([#15857](https://github.com/tailwindlabs/tailwindcss/pull/15857))
 - Disable bare value suggestions when not using the `--spacing` variable ([#15857](https://github.com/tailwindlabs/tailwindcss/pull/15857))
 - Ensure suggested classes are properly sorted ([#15857](https://github.com/tailwindlabs/tailwindcss/pull/15857))
+- Don’t look at ignore files outside initialized repos ([#15941](https://github.com/tailwindlabs/tailwindcss/pull/15941))
 - _Upgrade_: Ensure JavaScript config files on different drives are correctly migrated ([#15927](https://github.com/tailwindlabs/tailwindcss/pull/15927))
 
 ## [4.0.0] - 2025-01-21
diff --git a/crates/oxide/src/scanner/allowed_paths.rs b/crates/oxide/src/scanner/allowed_paths.rs
index 8a584d06fb2c..b906335f8979 100644
--- a/crates/oxide/src/scanner/allowed_paths.rs
+++ b/crates/oxide/src/scanner/allowed_paths.rs
@@ -33,17 +33,11 @@ pub fn resolve_allowed_paths(root: &Path) -> impl Iterator<Item = DirEntry> {
 
 #[tracing::instrument(skip_all)]
 pub fn resolve_paths(root: &Path) -> impl Iterator<Item = DirEntry> {
-    WalkBuilder::new(root)
-        .hidden(false)
-        .require_git(false)
-        .build()
-        .filter_map(Result::ok)
+    create_walk_builder(root).build().filter_map(Result::ok)
 }
 
 pub fn read_dir(root: &Path, depth: Option<usize>) -> impl Iterator<Item = DirEntry> {
-    WalkBuilder::new(root)
-        .hidden(false)
-        .require_git(false)
+    create_walk_builder(root)
         .max_depth(depth)
         .filter_entry(move |entry| match entry.file_type() {
             Some(file_type) if file_type.is_dir() => match entry.file_name().to_str() {
@@ -59,6 +53,61 @@ pub fn read_dir(root: &Path, depth: Option<usize>) -> impl Iterator<Item = DirEn
         .filter_map(Result::ok)
 }
 
+fn create_walk_builder(root: &Path) -> WalkBuilder {
+    let mut builder = WalkBuilder::new(root);
+
+    // Scan hidden files / directories
+    builder.hidden(false);
+
+    // By default, allow .gitignore files to be used regardless of whether or not
+    // a .git directory is present. This is an optimization for when projects
+    // are first created and may not be in a git repo yet.
+    builder.require_git(false);
+
+    // Don't descend into .git directories inside the root folder
+    // This is necessary when `root` contains the `.git` dir.
+    builder.filter_entry(|entry| entry.file_name() != ".git");
+
+    // If we are in a git repo then require it to ensure that only rules within
+    // the repo are used. For example, we don't want to consider a .gitignore file
+    // in the user's home folder if we're in a git repo.
+    //
+    // The alternative is using a call like `.parents(false)` but that will
+    // prevent looking at parent directories for .gitignore files from within
+    // the repo and that's not what we want.
+    //
+    // For example, in a project with this structure:
+    //
+    // home
+    // .gitignore
+    //  my-project
+    //   .gitignore
+    //   apps
+    //     .gitignore
+    //     web
+    //       {root}
+    //
+    // We do want to consider all .gitignore files listed:
+    // - home/.gitignore
+    // - my-project/.gitignore
+    // - my-project/apps/.gitignore
+    //
+    // However, if a repo is initialized inside my-project then only the following
+    // make sense for consideration:
+    // - my-project/.gitignore
+    // - my-project/apps/.gitignore
+    //
+    // Setting the require_git(true) flag conditionally allows us to do this.
+    for parent in root.ancestors() {
+        if parent.join(".git").exists() {
+            builder.require_git(true);
+            break;
+        }
+    }
+
+    builder
+}
+
 pub fn is_allowed_content_path(path: &Path) -> bool {
     // Skip known ignored files
     if path
diff --git a/crates/oxide/tests/scanner.rs b/crates/oxide/tests/scanner.rs
index cdec9a44dd26..e2bfdf37e558 100644
--- a/crates/oxide/tests/scanner.rs
+++ b/crates/oxide/tests/scanner.rs
@@ -586,4 +586,121 @@ mod scanner {
             ]
         );
     }
+
+    #[test]
+    fn skips_ignore_files_outside_of_a_repo() {
+        // Create a temporary working directory
+        let dir = tempdir().unwrap().into_path();
+
+        // Create files
+        create_files_in(
+            &dir,
+            &[
+                // This file should always be picked up
+                ("home/project/apps/web/index.html", "content-['index.html']"),
+                // Set up various ignore rules
+                ("home/.gitignore", "ignore-home.html"),
+                ("home/project/.gitignore", "ignore-project.html"),
+                ("home/project/apps/.gitignore", "ignore-apps.html"),
+                ("home/project/apps/web/.gitignore", "ignore-web.html"),
+                // Some of these should be ignored depending on which dir is the repo root
+                (
+                    "home/project/apps/web/ignore-home.html",
+                    "content-['ignore-home.html']",
+                ),
+                (
+                    "home/project/apps/web/ignore-project.html",
+                    "content-['ignore-project.html']",
+                ),
+                (
+                    "home/project/apps/web/ignore-apps.html",
+                    "content-['ignore-apps.html']",
+                ),
+                (
+                    "home/project/apps/web/ignore-web.html",
+                    "content-['ignore-web.html']",
+                ),
+            ],
+        );
+
+        let sources = vec![GlobEntry {
+            base: dir
+                .join("home/project/apps/web")
+                .to_string_lossy()
+                .to_string(),
+            pattern: "**/*".to_owned(),
+        }];
+
+        let candidates = Scanner::new(Some(sources.clone())).scan();
+
+        // All ignore files are applied because there's no git repo
+        assert_eq!(candidates, vec!["content-['index.html']".to_owned(),]);
+
+        // Initialize `home` as a git repository and scan again
+        // The results should be the same as before
+        _ = Command::new("git")
+            .arg("init")
+            .current_dir(dir.join("home"))
+            .output();
+        let candidates = Scanner::new(Some(sources.clone())).scan();
+
+        assert_eq!(candidates, vec!["content-['index.html']".to_owned(),]);
+
+        // Drop the .git folder
+        fs::remove_dir_all(dir.join("home/.git")).unwrap();
+
+        // Initialize `home/project` as a git repository and scan again
+        _ = Command::new("git")
+            .arg("init")
+            .current_dir(dir.join("home/project"))
+            .output();
+        let candidates = Scanner::new(Some(sources.clone())).scan();
+
+        assert_eq!(
+            candidates,
+            vec![
+                "content-['ignore-home.html']".to_owned(),
+                "content-['index.html']".to_owned(),
+            ]
+        );
+
+        // Drop the .git folder
+        fs::remove_dir_all(dir.join("home/project/.git")).unwrap();
+
+        // Initialize `home/project/apps` as a git repository and scan again
+        _ = Command::new("git")
+            .arg("init")
+            .current_dir(dir.join("home/project/apps"))
+            .output();
+        let candidates = Scanner::new(Some(sources.clone())).scan();
+
+        assert_eq!(
+            candidates,
+            vec![
+                "content-['ignore-home.html']".to_owned(),
+                "content-['ignore-project.html']".to_owned(),
+                "content-['index.html']".to_owned(),
+            ]
+        );
+
+        // Drop the .git folder
+        fs::remove_dir_all(dir.join("home/project/apps/.git")).unwrap();
+
+        // Initialize `home/project/apps` as a git repository and scan again
+        _ = Command::new("git")
+            .arg("init")
+            .current_dir(dir.join("home/project/apps/web"))
+            .output();
+        let candidates = Scanner::new(Some(sources.clone())).scan();
+
+        assert_eq!(
+            candidates,
+            vec![
+                "content-['ignore-apps.html']".to_owned(),
+                "content-['ignore-home.html']".to_owned(),
+                "content-['ignore-project.html']".to_owned(),
+                "content-['index.html']".to_owned(),
+            ]
+        );
+    }
 }
diff --git a/integrations/cli/index.test.ts b/integrations/cli/index.test.ts
index aff5b108994f..b47659a1320e 100644
--- a/integrations/cli/index.test.ts
+++ b/integrations/cli/index.test.ts
@@ -556,6 +556,83 @@ describe.each([
       ])
     },
   )
+
+  test(
+    'git ignore files outside of a repo are not considered',
+    {
+      fs: {
+        // Ignore everything in the "home" directory
+        'home/.gitignore': '*',
+
+        // Only ignore files called ignore-*.html in the actual git repo
+        'home/project/.gitignore': 'ignore-*.html',
+
+        'home/project/package.json': json`
+          {
+            "type": "module",
+            "dependencies": {
+              "tailwindcss": "workspace:^",
+              "@tailwindcss/cli": "workspace:^"
+            }
+          }
+        `,
+
+        'home/project/src/index.css': css` @import 'tailwindcss'; `,
+        'home/project/src/index.html': html`
+          <div
+            class="content-['index.html']"
+          ></div>
+        `,
+        'home/project/src/ignore-1.html': html`
+          <div
+            class="content-['ignore-1.html']"
+          ></div>
+        `,
+        'home/project/src/ignore-2.html': html`
+          <div
+            class="content-['ignore-2.html']"
+          ></div>
+        `,
+      },
+
+      installDependencies: false,
+    },
+    async ({ fs, root, exec }) => {
+      await exec(`pnpm install --ignore-workspace`, {
+        cwd: path.join(root, 'home/project'),
+      })
+
+      // No git repo = all ignore files are considered
+      await exec(`${command} --input src/index.css --output dist/out.css`, {
+        cwd: path.join(root, 'home/project'),
+      })
+
+      await fs.expectFileNotToContain('./home/project/dist/out.css', [
+        candidate`content-['index.html']`,
+        candidate`content-['ignore-1.html']`,
+        candidate`content-['ignore-2.html']`,
+      ])
+
+      // Make home/project a git repo
+      // Only ignore files within the repo are considered
+      await exec(`git init`, {
+        cwd: path.join(root, 'home/project'),
+      })
+
+      await exec(`${command} --input src/index.css --output dist/out.css`, {
+        cwd: path.join(root, 'home/project'),
+      })
+
+      await fs.expectFileToContain('./home/project/dist/out.css', [
+        candidate`content-['index.html']`,
+      ])
+
+      await fs.expectFileNotToContain('./home/project/dist/out.css', [
+        candidate`content-['ignore-1.html']`,
+        candidate`content-['ignore-2.html']`,
+      ])
+    },
+  )
 })
 
 test(
diff --git a/integrations/utils.ts b/integrations/utils.ts
index 4644ece49ab8..20f3fb49ec9e 100644
--- a/integrations/utils.ts
+++ b/integrations/utils.ts
@@ -32,6 +32,8 @@ interface TestConfig {
   fs: {
     [filePath: string]: string | Uint8Array
   }
+
+  installDependencies?: boolean
 }
 interface TestContext {
   root: string
@@ -382,14 +384,18 @@ export function test(
         await context.fs.write(filename, content)
       }
 
+      let shouldInstallDependencies = config.installDependencies ?? true
+
       try {
         // In debug mode, the directory is going to be inside the pnpm workspace
         // of the tailwindcss package. This means that `pnpm install` will run
         // pnpm install on the workspace instead (expect if the root dir defines
         // a separate workspace). We work around this by using the
         // `--ignore-workspace` flag.
-        let ignoreWorkspace = debug && !config.fs['pnpm-workspace.yaml']
-        await context.exec(`pnpm install${ignoreWorkspace ? ' --ignore-workspace' : ''}`)
+        if (shouldInstallDependencies) {
+          let ignoreWorkspace = debug && !config.fs['pnpm-workspace.yaml']
+          await context.exec(`pnpm install${ignoreWorkspace ? ' --ignore-workspace' : ''}`)
+        }
       } catch (error: any) {
         console.error(error)
         console.error(error.stdout?.toString())