src/main/java/de/zendric/app/xpensely_server/controller/ExpenseListController.java

@@ -80,6 +80,18 @@ public class ExpenseListController {
         return new ResponseEntity<>(HttpStatus.NO_CONTENT);
     }
 
+    @PutMapping("/{id}/rename")
+    public ResponseEntity<ExpenseList> rename(@PathVariable("id") Long id,
+            @RequestBody @Valid CreateExpenseListRequest request, Authentication authentication) {
+        AppUser user = authenticatedUserResolver.resolveCurrentUser(authentication);
+        Optional<ExpenseList> listOpt = expenseListService.findById(id);
+        if (listOpt.isEmpty())
+            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
+        assertOwner(user, listOpt.get());
+        ExpenseList renamed = expenseListService.renameList(id, request.getName());
+        return new ResponseEntity<>(renamed, HttpStatus.OK);
+    }
+
     @PostMapping("/{id}/add")
     public ResponseEntity<Expense> addExpenseToList(
             @PathVariable("id") Long expenseListId,

src/main/java/de/zendric/app/xpensely_server/services/ExpenseListService.java

@@ -39,6 +39,13 @@ public class ExpenseListService {
         repository.deleteById(id);
     }
 
+    public ExpenseList renameList(Long id, String newName) {
+        ExpenseList list = repository.findById(id)
+                .orElseThrow(() -> new ResourceNotFoundException("ExpenseList not found with id: " + id));
+        list.setName(newName);
+        return repository.save(list);
+    }
+
     public Optional<ExpenseList> findById(Long id) {
         return repository.findById(id);
     }

src/test/java/de/zendric/app/xpensely_Server/controller/ExpenseListControllerTest.java

@@ -207,6 +207,61 @@ class ExpenseListControllerTest {
                 .andExpect(status().isCreated());
     }
 
+    // --- Rename list ---
+
+    @Test
+    void renameList_owner_returns200WithRenamedList() throws Exception {
+        AppUser owner = new AppUser(); owner.setId(1L);
+        ExpenseList list = new ExpenseList(); list.setId(5L); list.setOwner(owner);
+        ExpenseList renamed = new ExpenseList(); renamed.setId(5L); renamed.setName("Groceries");
+
+        when(expenseListService.findById(5L)).thenReturn(Optional.of(list));
+        when(authenticatedUserResolver.resolveCurrentUser(any())).thenReturn(owner);
+        when(expenseListService.renameList(5L, "Groceries")).thenReturn(renamed);
+
+        mockMvc.perform(put("/api/expenselist/5/rename")
+                .contentType(MediaType.APPLICATION_JSON)
+                .content("{\"name\":\"Groceries\"}"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.name").value("Groceries"));
+    }
+
+    @Test
+    void renameList_nonOwner_returns403() throws Exception {
+        AppUser owner = new AppUser(); owner.setId(1L);
+        AppUser nonOwner = new AppUser(); nonOwner.setId(2L);
+        ExpenseList list = new ExpenseList(); list.setId(5L); list.setOwner(owner);
+
+        when(expenseListService.findById(5L)).thenReturn(Optional.of(list));
+        when(authenticatedUserResolver.resolveCurrentUser(any())).thenReturn(nonOwner);
+
+        mockMvc.perform(put("/api/expenselist/5/rename")
+                .contentType(MediaType.APPLICATION_JSON)
+                .content("{\"name\":\"Groceries\"}"))
+                .andExpect(status().isForbidden());
+    }
+
+    @Test
+    void renameList_blankName_returns400() throws Exception {
+        mockMvc.perform(put("/api/expenselist/5/rename")
+                .contentType(MediaType.APPLICATION_JSON)
+                .content("{\"name\":\"\"}"))
+                .andExpect(status().isBadRequest())
+                .andExpect(jsonPath("$.name").exists());
+    }
+
+    @Test
+    void renameList_notFound_returns404() throws Exception {
+        AppUser owner = new AppUser(); owner.setId(1L);
+        when(expenseListService.findById(9L)).thenReturn(Optional.empty());
+        when(authenticatedUserResolver.resolveCurrentUser(any())).thenReturn(owner);
+
+        mockMvc.perform(put("/api/expenselist/9/rename")
+                .contentType(MediaType.APPLICATION_JSON)
+                .content("{\"name\":\"Groceries\"}"))
+                .andExpect(status().isNotFound());
+    }
+
     // --- Duplicate-username invite guard ---
 
     @Test