diff --git a/README.md b/README.md
index 3028201..443344c 100644
--- a/README.md
+++ b/README.md
@@ -84,6 +84,11 @@ The following inputs can be used to control the action's behavior:
 * `ssh-agent-cmd`: Optional. Use this to specify a custom location for the `ssh-agent` binary.
 * `ssh-add-cmd`: Optional. Use this to specify a custom location for the `ssh-add` binary.
 * `git-cmd`: Optional. Use this to specify a custom location for the `git` binary.
+* `git-global-config`: Optional. Alter the global git config? If `false` only the git config in the current working directory will be altered. Defaults to `false`.
+  > [!IMPORTANT]
+  >
+  > Using this option also sets the `GIT_CONFIG_NOSYSTEM` environment variable.
+  > This prevents the global git config from being read from the system-wide configuration file.
 
 ## Exported variables
 
diff --git a/action.yml b/action.yml
index 8f32cc8..5699842 100644
--- a/action.yml
+++ b/action.yml
@@ -19,6 +19,9 @@ inputs:
     git-cmd:
         description: 'git command'
         required: false
+    git-global-config:
+        description: 'Alter the global git configuration?'
+        default: false
 runs:
     using: 'node20'
     main: 'dist/index.js'
diff --git a/cleanup.js b/cleanup.js
index 7c7b6a8..338608f 100644
--- a/cleanup.js
+++ b/cleanup.js
@@ -1,6 +1,11 @@
 const { execSync, execFileSync } = require("node:child_process");
 const { keyFilePrefix } = require("./consts.js");
-const { gitCmd, homePath, sshAgentCmd } = require("./paths.js");
+const {
+  gitCmd,
+  gitGlobalConfig,
+  homePath,
+  sshAgentCmd,
+} = require("./paths.js");
 const { alterGitConfigWithRetry } = require("./utils.js");
 const fs = require("node:fs");
 const os = require("node:os");
@@ -20,7 +25,7 @@ function restoreGitConfig(maxTries = 3) {
     console.log("Restoring git config");
     const result = alterGitConfigWithRetry(() => {
       return execSync(
-        `${gitCmd} config --global --get-regexp ".git@${keyFilePrefix}."`,
+        `${gitCmd} config${gitGlobalConfig} --get-regexp ".git@${keyFilePrefix}."`,
       );
     });
     const sections = result
@@ -34,7 +39,7 @@ function restoreGitConfig(maxTries = 3) {
         console.log(`Removing git config section ${section}`);
         alterGitConfigWithRetry(() => {
           return execSync(
-            `${gitCmd} config --global --remove-section ${section}`,
+            `${gitCmd} config${gitGlobalConfig} --remove-section ${section}`,
           );
         });
       }
diff --git a/dist/cleanup.js b/dist/cleanup.js
index fb798db..77bbe59 100644
--- a/dist/cleanup.js
+++ b/dist/cleanup.js
@@ -3432,6 +3432,7 @@ const defaults =
 const sshAgentCmdInput = core.getInput("ssh-agent-cmd");
 const sshAddCmdInput = core.getInput("ssh-add-cmd");
 const gitCmdInput = core.getInput("git-cmd");
+const gitGlobalConfigInput = core.getBooleanInput("git-global-config");
 
 module.exports = {
   homePath: defaults.homePath,
@@ -3439,6 +3440,7 @@ module.exports = {
     sshAgentCmdInput !== "" ? sshAgentCmdInput : defaults.sshAgentCmdDefault,
   sshAddCmd: sshAddCmdInput !== "" ? sshAddCmdInput : defaults.sshAddCmdDefault,
   gitCmd: gitCmdInput !== "" ? gitCmdInput : defaults.gitCmdDefault,
+  gitGlobalConfig: gitGlobalConfigInput ? " --global" : "",
 };
 
 
@@ -3660,7 +3662,12 @@ module.exports = require("util");
 var __webpack_exports__ = {};
 const { execSync, execFileSync } = __nccwpck_require__(421);
 const { keyFilePrefix } = __nccwpck_require__(334);
-const { gitCmd, homePath, sshAgentCmd } = __nccwpck_require__(644);
+const {
+  gitCmd,
+  gitGlobalConfig,
+  homePath,
+  sshAgentCmd,
+} = __nccwpck_require__(644);
 const { alterGitConfigWithRetry } = __nccwpck_require__(561);
 const fs = __nccwpck_require__(24);
 const os = __nccwpck_require__(161);
@@ -3680,7 +3687,7 @@ function restoreGitConfig(maxTries = 3) {
     console.log("Restoring git config");
     const result = alterGitConfigWithRetry(() => {
       return execSync(
-        `${gitCmd} config --global --get-regexp ".git@${keyFilePrefix}."`,
+        `${gitCmd} config${gitGlobalConfig} --get-regexp ".git@${keyFilePrefix}."`,
       );
     });
     const sections = result
@@ -3694,7 +3701,7 @@ function restoreGitConfig(maxTries = 3) {
         console.log(`Removing git config section ${section}`);
         alterGitConfigWithRetry(() => {
           return execSync(
-            `${gitCmd} config --global --remove-section ${section}`,
+            `${gitCmd} config${gitGlobalConfig} --remove-section ${section}`,
           );
         });
       }
diff --git a/dist/index.js b/dist/index.js
index 6804cab..82dba96 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -3432,6 +3432,7 @@ const defaults =
 const sshAgentCmdInput = core.getInput("ssh-agent-cmd");
 const sshAddCmdInput = core.getInput("ssh-add-cmd");
 const gitCmdInput = core.getInput("git-cmd");
+const gitGlobalConfigInput = core.getBooleanInput("git-global-config");
 
 module.exports = {
   homePath: defaults.homePath,
@@ -3439,6 +3440,7 @@ module.exports = {
     sshAgentCmdInput !== "" ? sshAgentCmdInput : defaults.sshAgentCmdDefault,
   sshAddCmd: sshAddCmdInput !== "" ? sshAddCmdInput : defaults.sshAddCmdDefault,
   gitCmd: gitCmdInput !== "" ? gitCmdInput : defaults.gitCmdDefault,
+  gitGlobalConfig: gitGlobalConfigInput ? " --global" : "",
 };
 
 
@@ -3670,7 +3672,13 @@ const core = __nccwpck_require__(484);
 const child_process = __nccwpck_require__(421);
 const fs = __nccwpck_require__(24);
 const crypto = __nccwpck_require__(598);
-const { homePath, sshAgentCmd, sshAddCmd, gitCmd } = __nccwpck_require__(644);
+const {
+  gitGlobalConfig,
+  homePath,
+  sshAgentCmd,
+  sshAddCmd,
+  gitCmd,
+} = __nccwpck_require__(644);
 const { keyFilePrefix } = __nccwpck_require__(334);
 const { alterGitConfigWithRetry } = __nccwpck_require__(561);
 
@@ -3750,17 +3758,17 @@ try {
 
       alterGitConfigWithRetry(() => {
         return child_process.execSync(
-          `${gitCmd} config --global --replace-all url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "https://github.com/${ownerAndRepo}"`,
+          `${gitCmd} config${gitGlobalConfig} --replace-all url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "https://github.com/${ownerAndRepo}"`,
         );
       });
       alterGitConfigWithRetry(() => {
         return child_process.execSync(
-          `${gitCmd} config --global --add url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "git@github.com:${ownerAndRepo}"`,
+          `${gitCmd} config${gitGlobalConfig} --add url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "git@github.com:${ownerAndRepo}"`,
         );
       });
       alterGitConfigWithRetry(() => {
         return child_process.execSync(
-          `${gitCmd} config --global --add url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "ssh://git@github.com/${ownerAndRepo}"`,
+          `${gitCmd} config${gitGlobalConfig} --add url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "ssh://git@github.com/${ownerAndRepo}"`,
         );
       });
 
@@ -3772,6 +3780,10 @@ try {
         `Added deploy-key mapping: Use identity '${homeSsh}/${keyFile}' for GitHub repository ${ownerAndRepo}`,
       );
     });
+  core.info(
+    "Setting GIT_CONFIG_NOSYSTEM. This prevents the global git config from being read from the system-wide configuration file.",
+  );
+  core.exportVariable("GIT_CONFIG_NOSYSTEM", "1");
 } catch (error) {
   if (error.code === "ENOENT") {
     console.log(
diff --git a/index.js b/index.js
index 0f3155f..2af33d5 100644
--- a/index.js
+++ b/index.js
@@ -2,7 +2,13 @@ const core = require("@actions/core");
 const child_process = require("node:child_process");
 const fs = require("node:fs");
 const crypto = require("node:crypto");
-const { homePath, sshAgentCmd, sshAddCmd, gitCmd } = require("./paths.js");
+const {
+  gitGlobalConfig,
+  homePath,
+  sshAgentCmd,
+  sshAddCmd,
+  gitCmd,
+} = require("./paths.js");
 const { keyFilePrefix } = require("./consts.js");
 const { alterGitConfigWithRetry } = require("./utils.js");
 
@@ -82,17 +88,17 @@ try {
 
       alterGitConfigWithRetry(() => {
         return child_process.execSync(
-          `${gitCmd} config --global --replace-all url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "https://github.com/${ownerAndRepo}"`,
+          `${gitCmd} config${gitGlobalConfig} --replace-all url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "https://github.com/${ownerAndRepo}"`,
         );
       });
       alterGitConfigWithRetry(() => {
         return child_process.execSync(
-          `${gitCmd} config --global --add url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "git@github.com:${ownerAndRepo}"`,
+          `${gitCmd} config${gitGlobalConfig} --add url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "git@github.com:${ownerAndRepo}"`,
         );
       });
       alterGitConfigWithRetry(() => {
         return child_process.execSync(
-          `${gitCmd} config --global --add url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "ssh://git@github.com/${ownerAndRepo}"`,
+          `${gitCmd} config${gitGlobalConfig} --add url."git@${keyFile}.github.com:${ownerAndRepo}".insteadOf "ssh://git@github.com/${ownerAndRepo}"`,
         );
       });
 
@@ -104,6 +110,10 @@ try {
         `Added deploy-key mapping: Use identity '${homeSsh}/${keyFile}' for GitHub repository ${ownerAndRepo}`,
       );
     });
+  core.info(
+    "Setting GIT_CONFIG_NOSYSTEM. This prevents the global git config from being read from the system-wide configuration file.",
+  );
+  core.exportVariable("GIT_CONFIG_NOSYSTEM", "1");
 } catch (error) {
   if (error.code === "ENOENT") {
     console.log(
diff --git a/paths.js b/paths.js
index 1d0fcf8..6f195c6 100644
--- a/paths.js
+++ b/paths.js
@@ -23,6 +23,7 @@ const defaults =
 const sshAgentCmdInput = core.getInput("ssh-agent-cmd");
 const sshAddCmdInput = core.getInput("ssh-add-cmd");
 const gitCmdInput = core.getInput("git-cmd");
+const gitGlobalConfigInput = core.getBooleanInput("git-global-config");
 
 module.exports = {
   homePath: defaults.homePath,
@@ -30,4 +31,5 @@ module.exports = {
     sshAgentCmdInput !== "" ? sshAgentCmdInput : defaults.sshAgentCmdDefault,
   sshAddCmd: sshAddCmdInput !== "" ? sshAddCmdInput : defaults.sshAddCmdDefault,
   gitCmd: gitCmdInput !== "" ? gitCmdInput : defaults.gitCmdDefault,
+  gitGlobalConfig: gitGlobalConfigInput ? " --global" : "",
 };