diff --git a/src/frontend/components/Sidebar.tsx b/src/frontend/components/Sidebar.tsx
index 922717d..2950104 100644
--- a/src/frontend/components/Sidebar.tsx
+++ b/src/frontend/components/Sidebar.tsx
@@ -2,6 +2,7 @@ import React, { useMemo, useState } from 'react';
 import { useNavigate } from 'react-router-dom';
 import {
   Button,
+  Checkbox,
   Label,
   Modal,
   ModalBody,
@@ -27,6 +28,7 @@ interface SidebarProps {
   onNewChat: () => void;
   onSelectChat: (chatId: string) => void;
   onDeleteChat: (chatId: string) => void;
+  onDeleteChats: (chatIds: string[]) => void;
   onDeleteAllChats: () => void;
   onRenameChat: (chatId: string, newTitle: string) => void;
 }
@@ -41,7 +43,7 @@ function SidebarComponent({
   onNewChat,
   onSelectChat,
   onDeleteChat,
-  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  onDeleteChats,
   onDeleteAllChats,
   onRenameChat,
 }: SidebarProps) {
@@ -51,7 +53,10 @@ function SidebarComponent({
   const [editingChat, setEditingChat] = useState<string | null>(null);
   const [editTitle, setEditTitle] = useState('');
   const [deletingChatId, setDeletingChatId] = useState<string | null>(null);
-
+  const [showDeleteAllDialog, setShowDeleteAllDialog] = useState(false);
+  const [isSelectionMode, setIsSelectionMode] = useState(false);
+  const [selectedChatIds, setSelectedChatIds] = useState<Set<string>>(new Set());
+  const [showDeleteSelectedDialog, setShowDeleteSelectedDialog] = useState(false);
 
   const filteredChats = useMemo(() => {
     const q = searchQuery.trim().toLowerCase();
@@ -62,6 +67,39 @@ function SidebarComponent({
     );
   }, [chatHistory, searchQuery]);
 
+  const allFilteredSelected =
+    filteredChats.length > 0 && filteredChats.every((chat) => selectedChatIds.has(chat.id));
+
+  const exitSelectionMode = () => {
+    setIsSelectionMode(false);
+    setSelectedChatIds(new Set());
+    setShowDeleteSelectedDialog(false);
+  };
+
+  const toggleChatSelected = (chatId: string) => {
+    setSelectedChatIds((prev) => {
+      const next = new Set(prev);
+      if (next.has(chatId)) {
+        next.delete(chatId);
+      } else {
+        next.add(chatId);
+      }
+      return next;
+    });
+  };
+
+  const toggleSelectAllFiltered = () => {
+    setSelectedChatIds((prev) => {
+      const next = new Set(prev);
+      if (allFilteredSelected) {
+        filteredChats.forEach((chat) => next.delete(chat.id));
+      } else {
+        filteredChats.forEach((chat) => next.add(chat.id));
+      }
+      return next;
+    });
+  };
+
   const handleRename = (chatId: string, title: string) => {
     setEditingChat(chatId);
     setEditTitle(title);
@@ -73,6 +111,12 @@ function SidebarComponent({
     setEditTitle('');
   };
 
+  const confirmDeleteSelected = () => {
+    const ids = [...selectedChatIds];
+    onDeleteChats(ids);
+    exitSelectionMode();
+  };
+
   return (
     <div className="flex flex-col h-full min-h-0 bg-sidebar border-r border-sidebar-border text-sidebar-foreground">
       {/* New Chat button */}
@@ -94,9 +138,67 @@ function SidebarComponent({
         </div>
       )}
 
-      {/* Separator + label */}
+      {/* Separator + label / selection toolbar */}
       <div className="shrink-0 px-3 pt-3 pb-1.5">
-        <p className="text-xs font-medium text-muted-foreground uppercase tracking-wider">Recent chats</p>
+        {isSelectionMode ? (
+          <div className="flex items-center justify-between gap-2">
+            <div className="flex items-center gap-2 min-w-0">
+              <Checkbox
+                id="select-all-chats"
+                isChecked={allFilteredSelected}
+                onChange={toggleSelectAllFiltered}
+                aria-label="Select all visible chats"
+              />
+              <p className="text-xs font-medium text-muted-foreground truncate">
+                {selectedChatIds.size} selected
+              </p>
+            </div>
+            <div className="flex items-center gap-2 shrink-0">
+              <button
+                type="button"
+                onClick={() => selectedChatIds.size > 0 && setShowDeleteSelectedDialog(true)}
+                disabled={selectedChatIds.size === 0}
+                className="text-xs text-destructive hover:text-destructive/80 disabled:opacity-40 disabled:cursor-not-allowed transition-colors"
+                aria-label={`Delete ${selectedChatIds.size} selected chats`}
+              >
+                Delete
+              </button>
+              <button
+                type="button"
+                onClick={exitSelectionMode}
+                className="text-xs text-muted-foreground hover:text-foreground transition-colors"
+              >
+                Cancel
+              </button>
+            </div>
+          </div>
+        ) : (
+          <div className="flex items-center justify-between gap-2">
+            <p className="text-xs font-medium text-muted-foreground uppercase tracking-wider">
+              Recent chats
+            </p>
+            {chatHistory.length > 0 && (
+              <div className="flex items-center gap-2">
+                <button
+                  type="button"
+                  onClick={() => setIsSelectionMode(true)}
+                  className="text-xs text-muted-foreground hover:text-foreground transition-colors"
+                  title="Select chats"
+                >
+                  Select
+                </button>
+                <button
+                  type="button"
+                  onClick={() => setShowDeleteAllDialog(true)}
+                  className="text-xs text-muted-foreground hover:text-destructive transition-colors"
+                  title="Delete all chats"
+                >
+                  Clear all
+                </button>
+              </div>
+            )}
+          </div>
+        )}
       </div>
 
       {/* Chat list */}
@@ -104,6 +206,7 @@ function SidebarComponent({
         className="flex-1 min-h-0 overflow-y-auto chat-scroll px-1.5"
         role="listbox"
         aria-label="Chat history"
+        aria-multiselectable={isSelectionMode}
       >
         {filteredChats.length === 0 ? (
           <div className="flex flex-col items-center justify-center py-10 px-4 text-center">
@@ -116,6 +219,7 @@ function SidebarComponent({
           <div className="space-y-0.5">
             {filteredChats.map((chat) => {
               const isActive = currentChatId === chat.id;
+              const isChecked = selectedChatIds.has(chat.id);
 
               const focusNeighbor = (delta: number) => {
                 const idx = filteredChats.findIndex((c) => c.id === chat.id);
@@ -127,7 +231,11 @@ function SidebarComponent({
               const onOptionKeyDown = (e: React.KeyboardEvent<HTMLDivElement>) => {
                 if (e.key === 'Enter' || e.key === ' ') {
                   e.preventDefault();
-                  onSelectChat(chat.id);
+                  if (isSelectionMode) {
+                    toggleChatSelected(chat.id);
+                  } else {
+                    onSelectChat(chat.id);
+                  }
                   return;
                 }
                 if (e.key === 'ArrowDown') {
@@ -147,16 +255,34 @@ function SidebarComponent({
                   id={`sidebar-chat-option-${chat.id}`}
                   role="option"
                   tabIndex={editingChat === chat.id ? -1 : 0}
-                  aria-selected={isActive}
+                  aria-selected={isSelectionMode ? isChecked : isActive}
                   className={cn(
                     'group flex items-center gap-2 px-2.5 py-2 rounded-lg cursor-pointer transition-colors outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2',
-                    isActive
+                    isSelectionMode && isChecked
                       ? 'bg-secondary text-foreground'
-                      : 'text-foreground/70 hover:bg-secondary/50 hover:text-foreground'
+                      : isActive && !isSelectionMode
+                        ? 'bg-secondary text-foreground'
+                        : 'text-foreground/70 hover:bg-secondary/50 hover:text-foreground'
                   )}
-                  onClick={() => onSelectChat(chat.id)}
+                  onClick={() => {
+                    if (isSelectionMode) {
+                      toggleChatSelected(chat.id);
+                    } else {
+                      onSelectChat(chat.id);
+                    }
+                  }}
                   onKeyDown={onOptionKeyDown}
                 >
+                  {isSelectionMode && (
+                    <Checkbox
+                      id={`select-chat-${chat.id}`}
+                      isChecked={isChecked}
+                      onChange={() => toggleChatSelected(chat.id)}
+                      onClick={(e) => e.stopPropagation()}
+                      aria-label={`Select chat: ${chat.title}`}
+                    />
+                  )}
+
                   {editingChat === chat.id ? (
                     <input
                       value={editTitle}
@@ -177,7 +303,7 @@ function SidebarComponent({
                   ) : (
                     <div className="flex-1 min-w-0">
                       <p className="text-sm truncate">{chat.title}</p>
-                      {isActive && activeSubAgent && (
+                      {isActive && activeSubAgent && !isSelectionMode && (
                         <div className="flex items-center gap-1.5 mt-0.5">
                           <Label
                             isCompact
@@ -191,7 +317,7 @@ function SidebarComponent({
                     </div>
                   )}
 
-                  {editingChat !== chat.id && (
+                  {!isSelectionMode && editingChat !== chat.id && (
                     <div className="flex shrink-0 gap-0.5 opacity-0 group-hover:opacity-100 transition-opacity">
                       <Button
                         variant="plain"
@@ -315,6 +441,54 @@ function SidebarComponent({
         </ModalFooter>
       </Modal>
 
+      <Modal
+        variant={ModalVariant.small}
+        isOpen={showDeleteSelectedDialog}
+        onClose={() => setShowDeleteSelectedDialog(false)}
+        aria-label="Delete selected chats confirmation"
+      >
+        <ModalHeader title="Delete selected chats?" />
+        <ModalBody>
+          This will permanently delete {selectedChatIds.size} selected conversation
+          {selectedChatIds.size === 1 ? '' : 's'}. This action cannot be undone.
+        </ModalBody>
+        <ModalFooter>
+          <Button variant="danger" onClick={confirmDeleteSelected}>
+            Delete selected
+          </Button>
+          <Button variant="link" onClick={() => setShowDeleteSelectedDialog(false)}>
+            Cancel
+          </Button>
+        </ModalFooter>
+      </Modal>
+
+      <Modal
+        variant={ModalVariant.small}
+        isOpen={showDeleteAllDialog}
+        onClose={() => setShowDeleteAllDialog(false)}
+        aria-label="Delete all chats confirmation"
+      >
+        <ModalHeader title="Delete all chats?" />
+        <ModalBody>
+          This will permanently delete all {chatHistory.length} conversations from your history.
+          This action cannot be undone.
+        </ModalBody>
+        <ModalFooter>
+          <Button
+            variant="danger"
+            onClick={() => {
+              onDeleteAllChats();
+              setShowDeleteAllDialog(false);
+            }}
+          >
+            Delete all
+          </Button>
+          <Button variant="link" onClick={() => setShowDeleteAllDialog(false)}>
+            Cancel
+          </Button>
+        </ModalFooter>
+      </Modal>
+
     </div>
   );
 }
diff --git a/src/frontend/components/layout/AppLayout.tsx b/src/frontend/components/layout/AppLayout.tsx
index a722121..7b818ac 100644
--- a/src/frontend/components/layout/AppLayout.tsx
+++ b/src/frontend/components/layout/AppLayout.tsx
@@ -99,7 +99,10 @@ export function AppLayout({ children }: AppLayoutProps) {
   const activeSubAgent = streamingState?.activeSubAgent ?? null;
 
   useEffect(() => {
-    const loadedChats = chatStorage.loadChats();
+    const deletedThreadIds = chatStorage.getDeletedThreadIds();
+    const loadedChats = chatStorage
+      .loadChats()
+      .filter((c) => !deletedThreadIds.has(c.id));
     if (loadedChats.length > 0) {
       const mapped: ChatItem[] = loadedChats.map((c) => ({
         ...c,
@@ -116,10 +119,12 @@ export function AppLayout({ children }: AppLayoutProps) {
     async function loadUserHistory() {
       try {
         dispatch(setLoadingThreads(true));
-        const history = await getAllThreadsByUserId(window.USER_DATA.preferred_username);
+        const deletedThreadIds = chatStorage.getDeletedThreadIds();
+        const history = (await getAllThreadsByUserId(window.USER_DATA.preferred_username))
+          .filter((t) => !deletedThreadIds.has(t.id));
 
         const backendIds = new Set(history.map((t) => t.id));
-        const local = chatsRef.current;
+        const local = chatsRef.current.filter((c) => !deletedThreadIds.has(c.id));
 
         const surviving = local.filter(
           (c) => backendIds.has(c.id) || isClientCreatedChat(c.id),
@@ -254,6 +259,7 @@ export function AppLayout({ children }: AppLayoutProps) {
 
   const handleDeleteChat = useCallback(
     (chatId: string) => {
+      chatStorage.markThreadDeleted(chatId);
       dispatch(deleteChat(chatId));
       dispatch(addToast({ title: 'Chat deleted', variant: 'success' }));
       if (location.pathname === `/chat/${chatId}`) {
@@ -267,6 +273,7 @@ export function AppLayout({ children }: AppLayoutProps) {
 
   const handleDeleteAllChats = useCallback(() => {
     const ids = chats.map((c) => c.id);
+    chatStorage.markThreadsDeleted(ids);
     dispatch(clearAllChats());
     chatStorage.clearChats();
     dispatch(addToast({ title: 'All chats deleted', variant: 'success' }));
@@ -274,6 +281,35 @@ export function AppLayout({ children }: AppLayoutProps) {
     ids.forEach((id) => deleteThread(id).catch(() => {}));
   }, [dispatch, chats, navigate]);
 
+  const handleDeleteChats = useCallback(
+    (chatIds: string[]) => {
+      if (chatIds.length === 0) return;
+
+      const idSet = new Set(chatIds);
+      chatStorage.markThreadsDeleted(chatIds);
+      chatIds.forEach((id) => dispatch(deleteChat(id)));
+
+      const remaining = chats.filter((c) => !idSet.has(c.id));
+      if (remaining.length === 0) {
+        chatStorage.clearChats();
+      }
+
+      dispatch(
+        addToast({
+          title: chatIds.length === 1 ? 'Chat deleted' : `${chatIds.length} chats deleted`,
+          variant: 'success',
+        })
+      );
+
+      if (currentChatId && idSet.has(currentChatId)) {
+        navigate(remaining.length > 0 ? `/chat/${remaining[0].id}` : '/');
+      }
+
+      chatIds.forEach((id) => deleteThread(id).catch(() => {}));
+    },
+    [dispatch, chats, navigate, currentChatId]
+  );
+
   const handleRenameChat = useCallback(
     (chatId: string, newTitle: string) => {
       dispatch(updateChat({ id: chatId, updates: { title: newTitle.trim() || 'Untitled Chat' } }));
@@ -350,6 +386,7 @@ export function AppLayout({ children }: AppLayoutProps) {
             onNewChat={handleNewChat}
             onSelectChat={handleSelectChat}
             onDeleteChat={handleDeleteChat}
+            onDeleteChats={handleDeleteChats}
             onDeleteAllChats={handleDeleteAllChats}
             onRenameChat={handleRenameChat}
           />
diff --git a/src/frontend/services/chatStorage.ts b/src/frontend/services/chatStorage.ts
index e4dab57..dbf2051 100644
--- a/src/frontend/services/chatStorage.ts
+++ b/src/frontend/services/chatStorage.ts
@@ -2,6 +2,7 @@ import { ChatItem } from '../types/chat';
 
 class ChatStorageService {
   private readonly CHATS_STORAGE_KEY = 'dataverse-ai-chats';
+  private readonly DELETED_THREADS_KEY = 'dataverse-ai-deleted-threads';
   private readonly MAX_CHATS = 50; // Limit to prevent localStorage bloat
 
   /**
@@ -88,6 +89,50 @@ class ChatStorageService {
     }
   }
 
+  /**
+   * Track a deleted thread so it is not restored from server history
+   */
+  markThreadDeleted(threadId: string): void {
+    try {
+      const deleted = this.getDeletedThreadIds();
+      deleted.add(threadId);
+      localStorage.setItem(this.DELETED_THREADS_KEY, JSON.stringify([...deleted]));
+    } catch (error) {
+      console.error('Error marking thread as deleted:', error);
+    }
+  }
+
+  /**
+   * Track multiple deleted threads at once
+   */
+  markThreadsDeleted(threadIds: string[]): void {
+    if (threadIds.length === 0) return;
+
+    try {
+      const deleted = this.getDeletedThreadIds();
+      threadIds.forEach((id) => deleted.add(id));
+      localStorage.setItem(this.DELETED_THREADS_KEY, JSON.stringify([...deleted]));
+    } catch (error) {
+      console.error('Error marking threads as deleted:', error);
+    }
+  }
+
+  /**
+   * Get IDs of threads the user has deleted from the UI
+   */
+  getDeletedThreadIds(): Set<string> {
+    try {
+      const stored = localStorage.getItem(this.DELETED_THREADS_KEY);
+      if (!stored) return new Set();
+
+      const parsed: string[] = JSON.parse(stored);
+      return new Set(parsed.filter(Boolean));
+    } catch (error) {
+      console.error('Error loading deleted thread IDs:', error);
+      return new Set();
+    }
+  }
+
   /**
    * Get storage usage info for debugging
    */