diff --git a/library/src/actions/index.ts b/library/src/actions/index.ts
index de638d32b..dbb0ad09e 100644
--- a/library/src/actions/index.ts
+++ b/library/src/actions/index.ts
@@ -80,6 +80,7 @@ export * from './trimEnd/index.ts';
 export * from './trimStart/index.ts';
 export * from './types.ts';
 export * from './ulid/index.ts';
+export * from './uniqueItems/index.ts';
 export * from './url/index.ts';
 export * from './uuid/index.ts';
 export * from './value/index.ts';
diff --git a/library/src/actions/uniqueItems/index.ts b/library/src/actions/uniqueItems/index.ts
new file mode 100644
index 000000000..d2cbf9748
--- /dev/null
+++ b/library/src/actions/uniqueItems/index.ts
@@ -0,0 +1 @@
+export * from './uniqueItems.ts';
diff --git a/library/src/actions/uniqueItems/uniqueItems.test-d.ts b/library/src/actions/uniqueItems/uniqueItems.test-d.ts
new file mode 100644
index 000000000..1251c87de
--- /dev/null
+++ b/library/src/actions/uniqueItems/uniqueItems.test-d.ts
@@ -0,0 +1,50 @@
+import { describe, expectTypeOf, test } from 'vitest';
+import type { InferInput, InferIssue, InferOutput } from '../../types/index.ts';
+import {
+  uniqueItems,
+  type UniqueItemsAction,
+  type UniqueItemsIssue,
+} from './uniqueItems.ts';
+
+describe('uniqueItems', () => {
+  describe('should return action object', () => {
+    test('with undefined message', () => {
+      type Action = UniqueItemsAction<unknown[], undefined>;
+      expectTypeOf(uniqueItems<unknown[]>()).toEqualTypeOf<Action>();
+      expectTypeOf(
+        uniqueItems<unknown[], undefined>(undefined)
+      ).toEqualTypeOf<Action>();
+    });
+
+    test('with string message', () => {
+      expectTypeOf(uniqueItems<unknown[], 'message'>('message')).toEqualTypeOf<
+        UniqueItemsAction<unknown[], 'message'>
+      >();
+    });
+
+    test('with function message', () => {
+      expectTypeOf(
+        uniqueItems<unknown[], () => string>(() => 'message')
+      ).toEqualTypeOf<UniqueItemsAction<unknown[], () => string>>();
+    });
+  });
+
+  describe('should infer correct types', () => {
+    type Input = [1, 'two', { value: 'three' }];
+    type Action = UniqueItemsAction<Input, undefined>;
+
+    test('of input', () => {
+      expectTypeOf<InferInput<Action>>().toEqualTypeOf<Input>();
+    });
+
+    test('of output', () => {
+      expectTypeOf<InferOutput<Action>>().toEqualTypeOf<Input>();
+    });
+
+    test('of issue', () => {
+      expectTypeOf<InferIssue<Action>>().toEqualTypeOf<
+        UniqueItemsIssue<Input>
+      >();
+    });
+  });
+});
diff --git a/library/src/actions/uniqueItems/uniqueItems.test.ts b/library/src/actions/uniqueItems/uniqueItems.test.ts
new file mode 100644
index 000000000..e35611b66
--- /dev/null
+++ b/library/src/actions/uniqueItems/uniqueItems.test.ts
@@ -0,0 +1,137 @@
+import { describe, expect, test } from 'vitest';
+import type { StringIssue } from '../../schemas/index.ts';
+import type { PartialDataset } from '../../types/dataset.ts';
+import { expectNoActionIssue } from '../../vitest/index.ts';
+import {
+  uniqueItems,
+  type UniqueItemsAction,
+  type UniqueItemsIssue,
+} from './uniqueItems.ts';
+
+describe('uniqueItems', () => {
+  describe('should return action object', () => {
+    const baseAction: Omit<UniqueItemsAction<unknown[], never>, 'message'> = {
+      kind: 'validation',
+      type: 'unique_items',
+      reference: uniqueItems,
+      expects: null,
+      async: false,
+      '~validate': expect.any(Function),
+    };
+
+    test('with undefined message', () => {
+      const action: UniqueItemsAction<unknown[], undefined> = {
+        ...baseAction,
+        message: undefined,
+      };
+      expect(uniqueItems()).toStrictEqual(action);
+      expect(uniqueItems<unknown[], undefined>(undefined)).toStrictEqual(
+        action
+      );
+    });
+
+    test('with string message', () => {
+      const message = 'message';
+      expect(uniqueItems<unknown[], 'message'>(message)).toStrictEqual({
+        ...baseAction,
+        message,
+      } satisfies UniqueItemsAction<unknown[], 'message'>);
+    });
+
+    test('with function message', () => {
+      const message = () => 'message';
+      expect(uniqueItems<unknown[], typeof message>(message)).toStrictEqual({
+        ...baseAction,
+        message,
+      } satisfies UniqueItemsAction<unknown[], typeof message>);
+    });
+  });
+
+  describe('should return dataset without issues', () => {
+    const action = uniqueItems<unknown[]>();
+
+    test('for untyped inputs', () => {
+      const issues: [StringIssue] = [
+        {
+          kind: 'schema',
+          type: 'string',
+          input: null,
+          expected: 'string',
+          received: 'null',
+          message: 'message',
+        },
+      ];
+      expect(
+        action['~validate']({ typed: false, value: null, issues }, {})
+      ).toStrictEqual({
+        typed: false,
+        value: null,
+        issues,
+      });
+    });
+
+    test('for empty array', () => {
+      expectNoActionIssue(action, [[]]);
+    });
+
+    test('for valid content', () => {
+      expectNoActionIssue(action, [[10, 11, 12, 13, 99]]);
+    });
+  });
+
+  describe('should return dataset with issues', () => {
+    const action = uniqueItems<number[], 'message'>('message');
+
+    const baseIssue: Omit<UniqueItemsIssue<number[]>, 'input' | 'received'> = {
+      kind: 'validation',
+      type: 'unique_items',
+      expected: null,
+      message: 'message',
+      requirement: undefined,
+      issues: undefined,
+      lang: undefined,
+      abortEarly: undefined,
+      abortPipeEarly: undefined,
+    };
+
+    test('for invalid(duplicated) content', () => {
+      const input = [5, 30, 2, 30, 8, 30];
+      expect(
+        action['~validate']({ typed: true, value: input }, {})
+      ).toStrictEqual({
+        typed: true,
+        value: input,
+        issues: [
+          {
+            ...baseIssue,
+            input: input[3],
+            received: `${input[3]}`,
+            path: [
+              {
+                type: 'array',
+                origin: 'value',
+                input,
+                key: 3,
+                value: input[3],
+              },
+            ],
+          },
+          {
+            ...baseIssue,
+            input: input[5],
+            received: `${input[5]}`,
+            path: [
+              {
+                type: 'array',
+                origin: 'value',
+                input,
+                key: 5,
+                value: input[5],
+              },
+            ],
+          },
+        ],
+      } satisfies PartialDataset<number[], UniqueItemsIssue<number[]>>);
+    });
+  });
+});
diff --git a/library/src/actions/uniqueItems/uniqueItems.ts b/library/src/actions/uniqueItems/uniqueItems.ts
new file mode 100644
index 000000000..24e7b15d3
--- /dev/null
+++ b/library/src/actions/uniqueItems/uniqueItems.ts
@@ -0,0 +1,115 @@
+import type {
+  BaseIssue,
+  BaseValidation,
+  ErrorMessage,
+} from '../../types/index.ts';
+import { _addIssue } from '../../utils/index.ts';
+import type { ArrayInput } from '../types.ts';
+
+/**
+ * Unique items issue type.
+ */
+export interface UniqueItemsIssue<TInput extends ArrayInput>
+  extends BaseIssue<TInput[number]> {
+  /**
+   * The issue kind.
+   */
+  readonly kind: 'validation';
+  /**
+   * The issue type.
+   */
+  readonly type: 'unique_items';
+  /**
+   * The expected input.
+   */
+  readonly expected: null;
+}
+
+/**
+ * Unique items action type.
+ */
+export interface UniqueItemsAction<
+  TInput extends ArrayInput,
+  TMessage extends ErrorMessage<UniqueItemsIssue<TInput>> | undefined,
+> extends BaseValidation<TInput, TInput, UniqueItemsIssue<TInput>> {
+  /**
+   * The action type.
+   */
+  readonly type: 'unique_items';
+  /**
+   * The action reference.
+   */
+  readonly reference: typeof uniqueItems;
+  /**
+   * The expected property.
+   */
+  readonly expects: null;
+  /**
+   * The error message.
+   */
+  readonly message: TMessage;
+}
+
+/**
+ * Creates an unique items validation action.
+ *
+ * @returns An unique items action.
+ */
+export function uniqueItems<TInput extends ArrayInput>(): UniqueItemsAction<
+  TInput,
+  undefined
+>;
+
+/**
+ * Creates an unique items validation action.
+ *
+ * @param message The error message.
+ *
+ * @returns An unique items action.
+ */
+export function uniqueItems<
+  TInput extends ArrayInput,
+  const TMessage extends ErrorMessage<UniqueItemsIssue<TInput>> | undefined,
+>(message: TMessage): UniqueItemsAction<TInput, TMessage>;
+
+export function uniqueItems(
+  message?: ErrorMessage<UniqueItemsIssue<unknown[]>>
+): UniqueItemsAction<
+  unknown[],
+  ErrorMessage<UniqueItemsIssue<unknown[]>> | undefined
+> {
+  return {
+    kind: 'validation',
+    type: 'unique_items',
+    reference: uniqueItems,
+    async: false,
+    expects: null,
+    message,
+    '~validate'(dataset, config) {
+      if (dataset.typed) {
+        const set = new Set<unknown>();
+
+        for (let index = 0; index < dataset.value.length; index++) {
+          const item = dataset.value[index];
+          if (set.has(item)) {
+            _addIssue(this, 'item', dataset, config, {
+              input: item,
+              path: [
+                {
+                  type: 'array',
+                  origin: 'value',
+                  input: dataset.value,
+                  key: index,
+                  value: item,
+                },
+              ],
+            });
+          } else {
+            set.add(item);
+          }
+        }
+      }
+      return dataset;
+    },
+  };
+}
diff --git a/packages/to-json-schema/src/convertAction.test.ts b/packages/to-json-schema/src/convertAction.test.ts
index c09b71ac8..c04cc39b3 100644
--- a/packages/to-json-schema/src/convertAction.test.ts
+++ b/packages/to-json-schema/src/convertAction.test.ts
@@ -490,4 +490,55 @@ describe('convertAction', () => {
       'The "transform" action cannot be converted to JSON Schema.'
     );
   });
+
+  test('should convert unique items action for array', () => {
+    expect(
+      convertAction(
+        {
+          type: 'array',
+        },
+        v.uniqueItems<v.ArrayInput>(),
+        undefined
+      )
+    ).toStrictEqual({
+      type: 'array',
+      uniqueItems: true,
+    });
+  });
+
+  test('should throw error for unique items action with invalid type', () => {
+    expect(() =>
+      convertAction({}, v.uniqueItems<v.ArrayInput>(), undefined)
+    ).toThrowError(
+      'The "unique_items" action is not supported on type "undefined".'
+    );
+    expect(() =>
+      convertAction(
+        { type: 'string' },
+        v.uniqueItems<v.ArrayInput>(),
+        undefined
+      )
+    ).toThrowError(
+      'The "unique_items" action is not supported on type "string".'
+    );
+  });
+
+  test('should force conversion for unique items action with invalid type', () => {
+    expect(
+      convertAction({}, v.uniqueItems<v.ArrayInput>(), { force: true })
+    ).toStrictEqual({
+      uniqueItems: true,
+    });
+    expect(console.warn).toHaveBeenLastCalledWith(
+      'The "unique_items" action is not supported on type "undefined".'
+    );
+    expect(
+      convertAction({ type: 'string' }, v.uniqueItems<v.ArrayInput>(), {
+        force: true,
+      })
+    ).toStrictEqual({ type: 'string', uniqueItems: true });
+    expect(console.warn).toHaveBeenLastCalledWith(
+      'The "unique_items" action is not supported on type "string".'
+    );
+  });
 });
diff --git a/packages/to-json-schema/src/convertAction.ts b/packages/to-json-schema/src/convertAction.ts
index 7852c1d37..9bcb7d93e 100644
--- a/packages/to-json-schema/src/convertAction.ts
+++ b/packages/to-json-schema/src/convertAction.ts
@@ -56,7 +56,11 @@ type Action =
       number,
       v.ErrorMessage<v.MultipleOfIssue<number, number>> | undefined
     >
-  | v.TitleAction<unknown, string>;
+  | v.TitleAction<unknown, string>
+  | v.UniqueItemsAction<
+      v.ArrayInput,
+      v.ErrorMessage<v.UniqueItemsIssue<v.ArrayInput>> | undefined
+    >;
 
 /**
  * Converts any supported Valibot action to the JSON Schema format.
@@ -191,6 +195,18 @@ export function convertAction(
       break;
     }
 
+    case 'unique_items': {
+      if (jsonSchema.type !== 'array') {
+        throwOrWarn(
+          `The "${valibotAction.type}" action is not supported on type "${jsonSchema.type}".`,
+          config
+        );
+      }
+      jsonSchema.uniqueItems = true;
+
+      break;
+    }
+
     default: {
       throwOrWarn(
         // @ts-expect-error