diff --git a/README.md b/README.md
index 3608c60..2bd41b5 100644
--- a/README.md
+++ b/README.md
@@ -24,12 +24,21 @@ jobs:
     steps:
       - uses: benelan/milestone-action@v3
         with:
-          farthest: true # remove this line to add the current milestone
-          overwrite: true # remove this line to keep an existing milestone
+          farthest: false # if true, add the milestone with the farthest due date.
+          overwrite: true # if true, allow overwriting an existing milestone.
+          single: false   # if true, add a milestone if it's the only one open, 
+                          # even if it doesn't have a due date.
 ```
 
 ## Changelog
 
+### [3.1.0](https://github.com/benelan/milestone-action/compare/v3.0.0...v3.1.0) (2024-02-10)
+
+#### Features
+
+- Add `single` option for workflows the consist of a single open milestone with
+  no due date.
+
 ### [3.0.0](https://github.com/benelan/milestone-action/compare/v2.0.0...v3.0.0) (2024-01-24)
 
 #### Breaking Changes
diff --git a/action.yml b/action.yml
index 5b9cccd..b4792fa 100644
--- a/action.yml
+++ b/action.yml
@@ -1,22 +1,26 @@
-name: 'Add Milestone By Due Date'
-description: 'Add the milestone with the current or farthest due date to pull requests and issues'
-author: 'Ben Elan'
+name: "Add Milestone By Due Date"
+description: "Add the milestone with the current or farthest due date to pull requests and issues"
+author: "Ben Elan"
 branding:
   icon: calendar
   color: green
 inputs:
   repo-token:
-    description: 'Token for the repository. Defaults to `{{ github.token }}`'
+    description: "Token for the repository. Defaults to `{{ github.token }}`"
     default: ${{ github.token }}
     required: false
   farthest:
-    description: 'Set this boolean to `true` if you want to add the milestone with the farthest due date. Defaults to `false`, which adds the current milestone.'
+    description: "Set this boolean to `true` if you want to add the milestone with the farthest due date. Defaults to `false`, which adds the current milestone."
     required: false
-    default: 'false'
+    default: "false"
   overwrite:
-    description: 'Set this boolean to `true` if you want the action to overwrite existing milestones on issues. Defaults to `false`, which ends the run if the issue already has a milestone.'
+    description: "Set this boolean to `true` if you want the action to overwrite existing milestones on issues. Defaults to `false`, which ends the run if the issue already has a milestone."
     required: false
-    default: 'false'
+    default: "false"
+  single:
+    description: "Set this boolean to `true` if you only have a single milestone open at a time but don't set the due date. Defaults to `false`, which will not select a milestone if it doesn't have a due date, even if there is only one milestone open."
+    required: false
+    default: "false"
 runs:
-  using: 'node20'
-  main: 'dist/index.js'
+  using: "node20"
+  main: "dist/index.js"
diff --git a/dist/index.js b/dist/index.js
index aaf33b1..94bac39 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -28925,6 +28925,7 @@ async function run() {
         }
         const farthest = (0, core_1.getBooleanInput)("farthest");
         const overwrite = (0, core_1.getBooleanInput)("overwrite");
+        const single = (0, core_1.getBooleanInput)("single");
         const token = (0, core_1.getInput)("repo-token");
         const octokit = (0, github_1.getOctokit)(token);
         if (!overwrite && (issue?.milestone || pull_request?.milestone)) {
@@ -28942,6 +28943,16 @@ async function run() {
             (0, core_1.warning)("Exit: there are no open milestones in this repo.");
             process.exit(0);
         }
+        if (single && milestones.length === 1) {
+            await octokit.rest.issues.update({
+                ...repo,
+                issue_number,
+                milestone: milestones[0].number,
+            });
+            (0, core_1.notice)(`Success: the issue or pull request was added to the "${milestones[0]?.title}" milestone.`);
+            (0, core_1.setOutput)("milestone", milestones[0]);
+            process.exit(0);
+        }
         const currentDate = new Date(Date.now());
         currentDate.setUTCHours(0, 0, 0, 0);
         for (const milestone of milestones) {
diff --git a/src/main.ts b/src/main.ts
index 2420448..011ada6 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -24,6 +24,7 @@ export async function run(): Promise<void> {
 
     const farthest = getBooleanInput("farthest");
     const overwrite = getBooleanInput("overwrite");
+    const single = getBooleanInput("single");
 
     const token = getInput("repo-token");
     const octokit = getOctokit(token);
@@ -48,6 +49,21 @@ export async function run(): Promise<void> {
       process.exit(0);
     }
 
+    if (single && milestones.length === 1) {
+      await octokit.rest.issues.update({
+        ...repo,
+        issue_number,
+        milestone: milestones[0].number,
+      });
+
+      notice(
+        `Success: the issue or pull request was added to the "${milestones[0]?.title}" milestone.`,
+      );
+
+      setOutput("milestone", milestones[0]);
+      process.exit(0);
+    }
+
     const currentDate = new Date(Date.now());
     currentDate.setUTCHours(0, 0, 0, 0);