diff --git a/README.md b/README.md
index 289eae4..f4cb016 100644
--- a/README.md
+++ b/README.md
@@ -152,6 +152,40 @@ Raw OpenAPI specification (JSON):
 http://localhost:8080/v3/api-docs
 ```
 
+### Available endpoints
+
+#### Generate and persist random users
+
+```http
+GET /random-users?count=500
+```
+
+#### Update an existing user
+
+```http
+PUT /random-users/{id}
+Content-Type: application/json
+```
+
+Example body:
+
+```json
+{
+  "gender": "female",
+  "firstname": "Albert",
+  "lastname": "Bing",
+  "civility": "Mrs",
+  "email": "albert.bing@example.com",
+  "phone": "123456789",
+  "picture": "pic.jpg",
+  "nat": "FR"
+}
+```
+
+Responses:
+- `200` if the user was updated successfully
+- `404` if the user id does not exist
+
 ---
 
 ## 🔍 Monitoring (Actuator)
@@ -281,7 +315,7 @@ This project consumes the public **Random User Generator** API:
 - [x] [Add PostgreSQL database with docker](https://github.com/XPEHO/spring_boot_java_random_user/issues/6)
 - [X] [Add this endpoint get /user/random](https://github.com/XPEHO/spring_boot_java_random_user/issues/5)
 - [ ] [Add this endpoint get /user/{id}](https://github.com/XPEHO/spring_boot_java_random_user/issues/8)
-- [ ] [Add this endpoint put /user/{id}](https://github.com/XPEHO/spring_boot_java_random_user/issues/9)
+- [X] [Add this endpoint put /user/{id}](https://github.com/XPEHO/spring_boot_java_random_user/issues/9)
 - [ ] [Add this endpoint delete /user/{id}](https://github.com/XPEHO/spring_boot_java_random_user/issues/10)
 - [ ] [Add this endpoint post /user](https://github.com/XPEHO/spring_boot_java_random_user/issues/11)
 
diff --git a/src/main/java/com/xpeho/spring_boot_java_random_user/data/services/UserServiceImpl.java b/src/main/java/com/xpeho/spring_boot_java_random_user/data/services/UserServiceImpl.java
index 3dae4e3..adc4723 100644
--- a/src/main/java/com/xpeho/spring_boot_java_random_user/data/services/UserServiceImpl.java
+++ b/src/main/java/com/xpeho/spring_boot_java_random_user/data/services/UserServiceImpl.java
@@ -8,6 +8,7 @@
 import org.springframework.stereotype.Service;
 
 import java.util.List;
+import java.util.Optional;
 import java.util.stream.StreamSupport;
 
 @Service
@@ -29,4 +30,16 @@ public List<UserEntity> saveAll(List<UserEntity> users) {
             .map(userConverter::toDomain)
             .toList();
     }
+
+    @Override
+    public Optional<UserEntity> getById(long id) {
+        return userRepository.findById(id)
+            .map(userConverter::toDomain);
+    }
+
+    @Override
+    public UserEntity save(UserEntity user) {
+        User savedUser = userRepository.save(userConverter.toDao(user));
+        return userConverter.toDomain(savedUser);
+    }
 }
diff --git a/src/main/java/com/xpeho/spring_boot_java_random_user/domain/entities/UserRequest.java b/src/main/java/com/xpeho/spring_boot_java_random_user/domain/entities/UserRequest.java
new file mode 100644
index 0000000..69ffa3a
--- /dev/null
+++ b/src/main/java/com/xpeho/spring_boot_java_random_user/domain/entities/UserRequest.java
@@ -0,0 +1,12 @@
+package com.xpeho.spring_boot_java_random_user.domain.entities;
+
+public record UserRequest(
+    String gender,
+    String firstname,
+    String lastname,
+    String civility,
+    String email,
+    String phone,
+    String picture,
+    String nat
+) {}
diff --git a/src/main/java/com/xpeho/spring_boot_java_random_user/domain/exceptions/UserNotFoundException.java b/src/main/java/com/xpeho/spring_boot_java_random_user/domain/exceptions/UserNotFoundException.java
new file mode 100644
index 0000000..e53e627
--- /dev/null
+++ b/src/main/java/com/xpeho/spring_boot_java_random_user/domain/exceptions/UserNotFoundException.java
@@ -0,0 +1,7 @@
+package com.xpeho.spring_boot_java_random_user.domain.exceptions;
+
+public class UserNotFoundException extends RuntimeException {
+    public UserNotFoundException(long id) {
+        super("User not found with id: " + id);
+    }
+}
diff --git a/src/main/java/com/xpeho/spring_boot_java_random_user/domain/services/UserService.java b/src/main/java/com/xpeho/spring_boot_java_random_user/domain/services/UserService.java
index 2462da7..f09a8af 100644
--- a/src/main/java/com/xpeho/spring_boot_java_random_user/domain/services/UserService.java
+++ b/src/main/java/com/xpeho/spring_boot_java_random_user/domain/services/UserService.java
@@ -2,7 +2,12 @@
 
 import com.xpeho.spring_boot_java_random_user.domain.entities.UserEntity;
 import java.util.List;
+import java.util.Optional;
 
 public interface UserService {
     List<UserEntity> saveAll(List<UserEntity> users);
+
+    Optional<UserEntity> getById(long id);
+
+    UserEntity save(UserEntity user);
 }
diff --git a/src/main/java/com/xpeho/spring_boot_java_random_user/domain/usecases/UpdateRandomUserUseCase.java b/src/main/java/com/xpeho/spring_boot_java_random_user/domain/usecases/UpdateRandomUserUseCase.java
new file mode 100644
index 0000000..26a73f5
--- /dev/null
+++ b/src/main/java/com/xpeho/spring_boot_java_random_user/domain/usecases/UpdateRandomUserUseCase.java
@@ -0,0 +1,35 @@
+package com.xpeho.spring_boot_java_random_user.domain.usecases;
+
+import com.xpeho.spring_boot_java_random_user.domain.entities.UserEntity;
+import com.xpeho.spring_boot_java_random_user.domain.entities.UserRequest;
+import com.xpeho.spring_boot_java_random_user.domain.exceptions.UserNotFoundException;
+import com.xpeho.spring_boot_java_random_user.domain.services.UserService;
+import org.springframework.stereotype.Service;
+
+@Service
+public class UpdateRandomUserUseCase {
+    private final UserService userService;
+
+    public UpdateRandomUserUseCase(UserService userService) {
+        this.userService = userService;
+    }
+
+    public UserEntity execute(int id, UserRequest user) {
+        UserEntity existingUser = userService.getById(id)
+            .orElseThrow(() -> new UserNotFoundException(id));
+
+        UserEntity updatedUser = new UserEntity(
+            existingUser.id(),
+            user.gender(),
+            user.firstname(),
+            user.lastname(),
+            user.civility(),
+            user.email(),
+            user.phone(),
+            user.picture(),
+            user.nat()
+        );
+
+        return userService.save(updatedUser);
+    }
+}
diff --git a/src/main/java/com/xpeho/spring_boot_java_random_user/presentation/controllers/UserController.java b/src/main/java/com/xpeho/spring_boot_java_random_user/presentation/controllers/UserController.java
index 530f82d..622f434 100644
--- a/src/main/java/com/xpeho/spring_boot_java_random_user/presentation/controllers/UserController.java
+++ b/src/main/java/com/xpeho/spring_boot_java_random_user/presentation/controllers/UserController.java
@@ -1,11 +1,15 @@
 package com.xpeho.spring_boot_java_random_user.presentation.controllers;
 
+import com.xpeho.spring_boot_java_random_user.domain.entities.UserRequest;
 import org.springframework.http.ResponseEntity;
 import java.util.List;
 import com.xpeho.spring_boot_java_random_user.domain.entities.UserEntity;
 import jakarta.validation.constraints.Max;
 import jakarta.validation.constraints.Min;
 import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PutMapping;
+import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestParam;
 
@@ -37,4 +41,22 @@ ResponseEntity<List<UserEntity>> getRandomUsers(
         @Max(5000)
         int count
     );
+    @PutMapping("/{id}")
+    @Operation(
+            summary = "Modify a random user",
+            description = "Giving a random user id, modify the content of the user",
+            parameters = {
+                    @Parameter(name = "id", description = "id of the requested user"),
+                    @Parameter(name= "UserEntity", description = "changeable parameters")
+            }
+    )
+    @ApiResponse(responseCode = "200", description = "User successfully modified and saved")
+    @ApiResponse(responseCode = "404", description = "The requested user does not exist")
+    @ApiResponse(responseCode = "500", description = "Internal server error")
+    ResponseEntity<UserEntity> updateRandomUser(
+            @PathVariable
+            int id,
+            @RequestBody
+            UserRequest user
+    );
 }
diff --git a/src/main/java/com/xpeho/spring_boot_java_random_user/presentation/handlers/UserHandler.java b/src/main/java/com/xpeho/spring_boot_java_random_user/presentation/handlers/UserHandler.java
index 50f860a..49a6203 100644
--- a/src/main/java/com/xpeho/spring_boot_java_random_user/presentation/handlers/UserHandler.java
+++ b/src/main/java/com/xpeho/spring_boot_java_random_user/presentation/handlers/UserHandler.java
@@ -1,7 +1,10 @@
 package com.xpeho.spring_boot_java_random_user.presentation.handlers;
 
 import com.xpeho.spring_boot_java_random_user.domain.entities.UserEntity;
+import com.xpeho.spring_boot_java_random_user.domain.entities.UserRequest;
+import com.xpeho.spring_boot_java_random_user.domain.exceptions.UserNotFoundException;
 import com.xpeho.spring_boot_java_random_user.domain.usecases.FetchAndSaveRandomUsersUseCase;
+import com.xpeho.spring_boot_java_random_user.domain.usecases.UpdateRandomUserUseCase;
 import com.xpeho.spring_boot_java_random_user.presentation.controllers.UserController;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -20,9 +23,14 @@ public class UserHandler implements UserController {
     private static final Logger logger = LoggerFactory.getLogger(UserHandler.class);
     
     private final FetchAndSaveRandomUsersUseCase fetchAndSaveRandomUsersUseCase;
+    private final UpdateRandomUserUseCase updateRandomUserUseCase;
 
-    public UserHandler(FetchAndSaveRandomUsersUseCase fetchAndSaveRandomUsersUseCase) {
+    public UserHandler(
+            FetchAndSaveRandomUsersUseCase fetchAndSaveRandomUsersUseCase,
+            UpdateRandomUserUseCase updateRandomUserUseCase
+    ) {
         this.fetchAndSaveRandomUsersUseCase = fetchAndSaveRandomUsersUseCase;
+        this.updateRandomUserUseCase = updateRandomUserUseCase;
     }
 
     @Override
@@ -36,4 +44,15 @@ public ResponseEntity<List<UserEntity>> getRandomUsers(int count) {
                         .body(emptyList());
             }
     }
-}
\ No newline at end of file
+    @Override
+    public ResponseEntity<UserEntity> updateRandomUser(int id, UserRequest user) {
+        try {
+            UserEntity savedUser = updateRandomUserUseCase.execute(id, user);
+            return ResponseEntity.ok(savedUser);
+        } catch (UserNotFoundException e) {
+            logger.warn("warning: the requested user does not exist : {}", e.getMessage(), e);
+            return ResponseEntity.status(HttpStatus.NOT_FOUND).build();
+        }
+    }
+
+}
diff --git a/src/test/java/com/xpeho/spring_boot_java_random_user/data/services/UserServiceImplTest.java b/src/test/java/com/xpeho/spring_boot_java_random_user/data/services/UserServiceImplTest.java
new file mode 100644
index 0000000..2b86838
--- /dev/null
+++ b/src/test/java/com/xpeho/spring_boot_java_random_user/data/services/UserServiceImplTest.java
@@ -0,0 +1,88 @@
+package com.xpeho.spring_boot_java_random_user.data.services;
+
+import com.xpeho.spring_boot_java_random_user.data.converters.UserConverter;
+import com.xpeho.spring_boot_java_random_user.data.models.db.User;
+import com.xpeho.spring_boot_java_random_user.data.sources.database.UserRepository;
+import com.xpeho.spring_boot_java_random_user.domain.entities.UserEntity;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+class UserServiceImplTest {
+    private UserRepository userRepository;
+    private UserConverter userConverter;
+    private UserServiceImpl userService;
+
+    @BeforeEach
+    void setUp() {
+        userRepository = mock(UserRepository.class);
+        userConverter = mock(UserConverter.class);
+        userService = new UserServiceImpl(userRepository, userConverter);
+    }
+
+    @Test
+    @DisplayName("Should return mapped user when id exists")
+    void shouldReturnMappedUserWhenIdExists() {
+        User dao = new User();
+        dao.setId(1L);
+        dao.setFirstname("John");
+
+        UserEntity expected = new UserEntity(1L, "male", "John", "Doe", "Mr", "john@doe.com", "1234", "pic.jpg", "FR");
+
+        when(userRepository.findById(1L)).thenReturn(Optional.of(dao));
+        when(userConverter.toDomain(dao)).thenReturn(expected);
+
+        Optional<UserEntity> result = userService.getById(1L);
+
+        assertTrue(result.isPresent());
+        assertEquals(expected, result.get());
+        verify(userRepository).findById(1L);
+        verify(userConverter).toDomain(dao);
+    }
+
+    @Test
+    @DisplayName("Should return empty optional when id does not exist")
+    void shouldReturnEmptyOptionalWhenIdDoesNotExist() {
+        when(userRepository.findById(2L)).thenReturn(Optional.empty());
+
+        Optional<UserEntity> result = userService.getById(2L);
+
+        assertTrue(result.isEmpty());
+        verify(userRepository).findById(2L);
+    }
+
+    @Test
+    @DisplayName("Should save mapped user and return mapped domain entity")
+    void shouldSaveMappedUserAndReturnMappedDomainEntity() {
+        UserEntity input = new UserEntity(3L, "female", "Alice", "Smith", "Mrs", "alice@smith.com", "5678", "new-pic.jpg", "US");
+
+        User daoToSave = new User();
+        daoToSave.setId(3L);
+        daoToSave.setFirstname("Alice");
+
+        User savedDao = new User();
+        savedDao.setId(3L);
+        savedDao.setFirstname("Alice");
+
+        UserEntity expected = new UserEntity(3L, "female", "Alice", "Smith", "Mrs", "alice@smith.com", "5678", "new-pic.jpg", "US");
+
+        when(userConverter.toDao(input)).thenReturn(daoToSave);
+        when(userRepository.save(daoToSave)).thenReturn(savedDao);
+        when(userConverter.toDomain(savedDao)).thenReturn(expected);
+
+        UserEntity result = userService.save(input);
+
+        assertEquals(expected, result);
+        verify(userConverter).toDao(input);
+        verify(userRepository).save(daoToSave);
+        verify(userConverter).toDomain(savedDao);
+    }
+}
diff --git a/src/test/java/com/xpeho/spring_boot_java_random_user/domain/usecases/UpdateRandomUserUseCaseTest.java b/src/test/java/com/xpeho/spring_boot_java_random_user/domain/usecases/UpdateRandomUserUseCaseTest.java
new file mode 100644
index 0000000..8aee528
--- /dev/null
+++ b/src/test/java/com/xpeho/spring_boot_java_random_user/domain/usecases/UpdateRandomUserUseCaseTest.java
@@ -0,0 +1,76 @@
+package com.xpeho.spring_boot_java_random_user.domain.usecases;
+
+import com.xpeho.spring_boot_java_random_user.domain.entities.UserEntity;
+import com.xpeho.spring_boot_java_random_user.domain.entities.UserRequest;
+import com.xpeho.spring_boot_java_random_user.domain.exceptions.UserNotFoundException;
+import com.xpeho.spring_boot_java_random_user.domain.services.UserService;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+class UpdateRandomUserUseCaseTest {
+    private UserService userService;
+    private UpdateRandomUserUseCase useCase;
+
+    @BeforeEach
+    void setUp() {
+        userService = mock(UserService.class);
+        useCase = new UpdateRandomUserUseCase(userService);
+    }
+
+    @Test
+    @DisplayName("Should update an existing user and preserve its id")
+    void shouldUpdateExistingUserAndPreserveItsId() {
+        UserEntity existingUser = new UserEntity(
+            42L, "male", "John", "Doe", "Mr", "john@doe.com", "1234", "pic.jpg", "FR"
+        );
+        UserRequest request = new UserRequest(
+            "female", "Alice", "Smith", "Mrs", "alice@smith.com", "5678", "new-pic.jpg", "US"
+        );
+        UserEntity savedUser = new UserEntity(
+            42L, "female", "Alice", "Smith", "Mrs", "alice@smith.com", "5678", "new-pic.jpg", "US"
+        );
+
+        when(userService.getById(42)).thenReturn(Optional.of(existingUser));
+        when(userService.save(new UserEntity(
+            42L, "female", "Alice", "Smith", "Mrs", "alice@smith.com", "5678", "new-pic.jpg", "US"
+        ))).thenReturn(savedUser);
+
+        UserEntity result = useCase.execute(42, request);
+
+        assertEquals(savedUser, result);
+        verify(userService).getById(42);
+        verify(userService).save(new UserEntity(
+            42L, "female", "Alice", "Smith", "Mrs", "alice@smith.com", "5678", "new-pic.jpg", "US"
+        ));
+    }
+
+    @Test
+    @DisplayName("Should throw when updating a user that does not exist")
+    void shouldThrowWhenUserDoesNotExist() {
+        UserRequest request = new UserRequest(
+            "female", "Alice", "Smith", "Mrs", "alice@smith.com", "5678", "new-pic.jpg", "US"
+        );
+
+        when(userService.getById(99)).thenReturn(Optional.empty());
+
+        UserNotFoundException exception = assertThrows(
+            UserNotFoundException.class,
+            () -> useCase.execute(99, request)
+        );
+
+        assertEquals("User not found with id: 99", exception.getMessage());
+        verify(userService).getById(99);
+        verify(userService, never()).save(any(UserEntity.class));
+    }
+}