diff --git a/frontend/src/App.jsx b/frontend/src/App.jsx
index 7e7b58a5b..32fc4b4f6 100644
--- a/frontend/src/App.jsx
+++ b/frontend/src/App.jsx
@@ -12,6 +12,7 @@ import { FullScreenLoader } from "./components/Preloader";
 import { ThemeProvider } from "./ThemeContext";
 import { PWAModeProvider } from "./PWAContext";
 import KeyboardShortcutsHelp from "@/components/KeyboardShortcutsHelp";
+import ImageLightbox from "@/components/ImageLightbox";
 import { ErrorBoundary } from "react-error-boundary";
 import ErrorBoundaryFallback from "./components/ErrorBoundaryFallback";
 
@@ -33,6 +34,7 @@ export default function App() {
                     <Outlet />
                     <ToastContainer />
                     <KeyboardShortcutsHelp />
+                    <ImageLightbox />
                   </I18nextProvider>
                 </PfpProvider>
               </LogoProvider>
diff --git a/frontend/src/components/ImageLightbox/index.jsx b/frontend/src/components/ImageLightbox/index.jsx
new file mode 100644
index 000000000..bd91cd076
--- /dev/null
+++ b/frontend/src/components/ImageLightbox/index.jsx
@@ -0,0 +1,115 @@
+import { useState, useEffect } from "react";
+import { createPortal } from "react-dom";
+import { X, CaretLeft, CaretRight } from "@phosphor-icons/react";
+
+const OPEN_EVENT = "open-image-lightbox";
+
+/**
+ * Opens the image lightbox from anywhere in the app.
+ * @param {{contentString: string, name: string}[]} images
+ * @param {number} initialIndex
+ */
+export function openImageLightbox(images, initialIndex = 0) {
+  window.dispatchEvent(
+    new CustomEvent(OPEN_EVENT, { detail: { images, initialIndex } })
+  );
+}
+
+export default function ImageLightbox() {
+  const [images, setImages] = useState(null);
+  const [currentIndex, setCurrentIndex] = useState(0);
+
+  useEffect(() => {
+    function handleOpen(e) {
+      setImages(e.detail.images);
+      setCurrentIndex(e.detail.initialIndex);
+    }
+    window.addEventListener(OPEN_EVENT, handleOpen);
+    return () => window.removeEventListener(OPEN_EVENT, handleOpen);
+  }, []);
+
+  function close() {
+    setImages(null);
+  }
+
+  function handlePrevious() {
+    setCurrentIndex((prev) => (prev > 0 ? prev - 1 : images.length - 1));
+  }
+
+  function handleNext() {
+    setCurrentIndex((prev) => (prev < images.length - 1 ? prev + 1 : 0));
+  }
+
+  useEffect(() => {
+    if (!images) return;
+    function handleKeyDown(e) {
+      if (e.key === "Escape") close();
+      else if (e.key === "ArrowLeft") handlePrevious();
+      else if (e.key === "ArrowRight") handleNext();
+    }
+    window.addEventListener("keydown", handleKeyDown);
+    return () => window.removeEventListener("keydown", handleKeyDown);
+  }, [images]);
+
+  if (!images || images.length === 0) return null;
+  const safeIndex = Math.min(currentIndex, images.length - 1);
+  const currentImage = images[safeIndex];
+  if (!currentImage) return null;
+
+  return createPortal(
+    <div
+      className="fixed inset-0 z-[9999] flex items-center justify-center bg-black/90"
+      onClick={close}
+    >
+      <button
+        type="button"
+        onClick={close}
+        className="absolute top-4 right-4 p-2 text-white light:text-white hover:text-white/70 transition-colors rounded-full bg-white/10 hover:bg-white/20 border-none cursor-pointer"
+        aria-label="Close lightbox"
+      >
+        <X size={24} weight="bold" />
+      </button>
+
+      {images.length > 1 && (
+        <>
+          <button
+            type="button"
+            onClick={(e) => {
+              e.stopPropagation();
+              handlePrevious();
+            }}
+            className="absolute left-4 p-3 text-white light:text-white hover:text-white/70 transition-colors rounded-full bg-white/10 hover:bg-white/20 border-none cursor-pointer"
+            aria-label="Previous image"
+          >
+            <CaretLeft size={24} weight="bold" />
+          </button>
+          <button
+            type="button"
+            onClick={(e) => {
+              e.stopPropagation();
+              handleNext();
+            }}
+            className="absolute right-4 p-3 text-white light:text-white hover:text-white/70 transition-colors rounded-full bg-white/10 hover:bg-white/20 border-none cursor-pointer"
+            aria-label="Next image"
+          >
+            <CaretRight size={24} weight="bold" />
+          </button>
+        </>
+      )}
+
+      <img
+        src={currentImage.contentString}
+        alt={currentImage.name || "attachment"}
+        className="max-w-[90vw] max-h-[90vh] object-contain"
+        onClick={(e) => e.stopPropagation()}
+      />
+
+      {images.length > 1 && (
+        <div className="absolute bottom-4 left-1/2 -translate-x-1/2 text-white/70 text-sm bg-black/50 px-3 py-1 rounded-full">
+          {safeIndex + 1} / {images.length}
+        </div>
+      )}
+    </div>,
+    document.getElementById("root")
+  );
+}
diff --git a/frontend/src/components/WorkspaceChat/ChatContainer/ChatHistory/HistoricalMessage/index.jsx b/frontend/src/components/WorkspaceChat/ChatContainer/ChatHistory/HistoricalMessage/index.jsx
index c6c581753..53a0d751f 100644
--- a/frontend/src/components/WorkspaceChat/ChatContainer/ChatHistory/HistoricalMessage/index.jsx
+++ b/frontend/src/components/WorkspaceChat/ChatContainer/ChatHistory/HistoricalMessage/index.jsx
@@ -19,6 +19,7 @@ import { useTranslation } from "react-i18next";
 import { Link } from "react-router-dom";
 import { chatQueryRefusalResponse } from "@/utils/chat";
 import HistoricalOutputs from "./HistoricalOutputs";
+import { openImageLightbox } from "@/components/ImageLightbox";
 
 const HistoricalMessage = ({
   uuid = v4(),
@@ -205,17 +206,27 @@ export default memo(
   }
 );
 
+/**
+ * Currently only renders image attachments as clickable thumbnails that open in the lightbox.
+ * Other attachment types may be supported here in the future.
+ */
 function ChatAttachments({ attachments = [] }) {
   if (!attachments.length) return null;
   return (
     <div className="flex flex-wrap gap-4 mt-4">
-      {attachments.map((item) => (
-        <img
-          alt={`Attachment: ${item.name}`}
+      {attachments.map((item, index) => (
+        <button
+          type="button"
           key={item.name}
-          src={item.contentString}
-          className="w-[120px] h-[120px] object-cover rounded-lg"
-        />
+          onClick={() => openImageLightbox(attachments, index)}
+          className="p-0 border-none bg-transparent cursor-pointer hover:opacity-80 transition-opacity"
+        >
+          <img
+            alt={`Attachment: ${item.name}`}
+            src={item.contentString}
+            className="w-[120px] h-[120px] object-cover rounded-lg"
+          />
+        </button>
       ))}
     </div>
   );
diff --git a/frontend/src/components/WorkspaceChat/ChatContainer/PromptInput/Attachments/index.jsx b/frontend/src/components/WorkspaceChat/ChatContainer/PromptInput/Attachments/index.jsx
index 6b1e2d1b3..d4e6f5bad 100644
--- a/frontend/src/components/WorkspaceChat/ChatContainer/PromptInput/Attachments/index.jsx
+++ b/frontend/src/components/WorkspaceChat/ChatContainer/PromptInput/Attachments/index.jsx
@@ -11,6 +11,7 @@ import {
   X,
 } from "@phosphor-icons/react";
 import { REMOVE_ATTACHMENT_EVENT } from "../../DnDWrapper";
+import { openImageLightbox } from "@/components/ImageLightbox";
 
 /**
  * @param {{attachments: import("../../DnDWrapper").Attachment[]}}
@@ -18,10 +19,25 @@ import { REMOVE_ATTACHMENT_EVENT } from "../../DnDWrapper";
  */
 export default function AttachmentManager({ attachments }) {
   if (attachments.length === 0) return null;
+
+  function handleImageClick(attachment) {
+    const imageAttachments = attachments
+      .filter((a) => a.type === "attachment" && a.contentString)
+      .map((a) => ({ contentString: a.contentString, name: a.file.name }));
+    const idx = imageAttachments.findIndex(
+      (img) => img.name === attachment.file?.name
+    );
+    if (idx !== -1) openImageLightbox(imageAttachments, idx);
+  }
+
   return (
     <div className="flex flex-wrap gap-2 mt-2 mb-4">
       {attachments.map((attachment) => (
-        <AttachmentItem key={attachment.uid} attachment={attachment} />
+        <AttachmentItem
+          key={attachment.uid}
+          attachment={attachment}
+          onImageClick={() => handleImageClick(attachment)}
+        />
       ))}
     </div>
   );
@@ -30,7 +46,7 @@ export default function AttachmentManager({ attachments }) {
 /**
  * @param {{attachment: import("../../DnDWrapper").Attachment}}
  */
-function AttachmentItem({ attachment }) {
+function AttachmentItem({ attachment, onImageClick }) {
   const { uid, file, status, error, document, type, contentString } =
     attachment;
   const { iconBgColor, Icon } = displayFromFile(file);
@@ -115,12 +131,18 @@ function AttachmentItem({ attachment }) {
               <X size={10} className="flex-shrink-0" />
             </button>
           </div>
-          <img
-            alt={`Preview of ${file.name}`}
-            src={contentString}
-            style={{ objectFit: "cover", objectPosition: "center" }}
-            className={`${iconBgColor} w-[40px] h-[40px] rounded-lg flex items-center justify-center`}
-          />
+          <button
+            type="button"
+            onClick={onImageClick}
+            className="p-0 border-none bg-transparent cursor-pointer"
+          >
+            <img
+              alt={`Preview of ${file.name}`}
+              src={contentString}
+              style={{ objectFit: "cover", objectPosition: "center" }}
+              className={`${iconBgColor} w-[40px] h-[40px] rounded-lg flex items-center justify-center`}
+            />
+          </button>
         </div>
       );
     }