diff --git a/src/renderer/components/modals/AboutDialog.tsx b/src/renderer/components/modals/AboutDialog.tsx
new file mode 100644
index 0000000..bd7c9ed
--- /dev/null
+++ b/src/renderer/components/modals/AboutDialog.tsx
@@ -0,0 +1,49 @@
+import { useEffect, useState } from 'react';
+import { Dialog, DialogContent, DialogDescription, DialogFooter, DialogHeader, DialogTitle } from '@/components/ui/dialog';
+import { Button } from '@/components/ui/button';
+import { ipc } from '@/lib/ipc';
+import { useAppStore } from '@/stores/app-store';
+
+export function AboutDialog() {
+  const closeModal = useAppStore((s) => s.closeModal);
+  const isOpen = useAppStore((s) => s.modal.kind) === 'about';
+  const [version, setVersion] = useState<string>('…');
+
+  useEffect(() => {
+    ipc.app.getVersion().then((r) => {
+      if (r.ok && typeof r.data === 'string') setVersion(r.data);
+    });
+  }, []);
+
+  return (
+    <Dialog open={isOpen} onOpenChange={(o) => !o && closeModal()}>
+      <DialogContent aria-describedby="about-desc">
+        <DialogHeader>
+          <DialogTitle>About MarkdownConverter</DialogTitle>
+          <DialogDescription id="about-desc">
+            Professional Markdown editor and universal file converter.
+          </DialogDescription>
+        </DialogHeader>
+        <div className="space-y-2 text-sm text-muted-foreground">
+          <p>Version: {version}</p>
+          <p>
+            <a
+              href="https://github.com/amitwh/markdown-converter"
+              className="text-brand hover:underline"
+              onClick={(e) => {
+                e.preventDefault();
+                ipc.app.openExternal('https://github.com/amitwh/markdown-converter');
+              }}
+            >
+              GitHub repository
+            </a>
+          </p>
+          <p className="text-xs">© ConcreteInfo. Licensed under MIT.</p>
+        </div>
+        <DialogFooter>
+          <Button onClick={closeModal}>Close</Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+}
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diff --git a/tests/component/modals/AboutDialog.test.tsx b/tests/component/modals/AboutDialog.test.tsx
new file mode 100644
index 0000000..8c0b752
--- /dev/null
+++ b/tests/component/modals/AboutDialog.test.tsx
@@ -0,0 +1,34 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { AboutDialog } from '@/components/modals/AboutDialog';
+import { useAppStore } from '@/stores/app-store';
+
+describe('AboutDialog', () => {
+  beforeEach(() => {
+    window.electronAPI = {
+      app: {
+        getVersion: vi.fn().mockResolvedValue('5.0.0'),
+        openExternal: vi.fn().mockResolvedValue({ ok: true }),
+      },
+    } as any;
+    // Reset store to about modal so dialog renders
+    useAppStore.setState({ modal: { kind: 'about' } } as any);
+  });
+
+  it('renders title and version', async () => {
+    render(<AboutDialog />);
+    expect(screen.getByText(/about markdownconverter/i)).toBeInTheDocument();
+    expect(await screen.findByText(/5\.0\.0/)).toBeInTheDocument();
+  });
+
+  it('closes when the close button is clicked', async () => {
+    render(<AboutDialog />);
+    // dialog-footer has the visible Close button; the X button also has sr-only "Close"
+    const closeButtons = await screen.findAllByRole('button', { name: /close/i });
+    const close = closeButtons[0];
+    await userEvent.click(close);
+    // closeModal sets modal.kind = null, so isOpen=false, Dialog unmounts
+    expect(screen.queryByRole('dialog')).not.toBeInTheDocument();
+  });
+});
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