diff --git a/frontend/src/lib/types.ts b/frontend/src/lib/types.ts
index d0b3576..2581bfe 100644
--- a/frontend/src/lib/types.ts
+++ b/frontend/src/lib/types.ts
@@ -1,4 +1,4 @@
-export type Theme = 'light' | 'dark' | 'system';
+export type Theme = 'light' | 'dark' | 'system' | 'neon';
 
 /** Lifecycle of the NIP-46 remote signer. */
 export type SignerPhase = 'stopped' | 'connecting' | 'connected';
diff --git a/frontend/src/screens/SettingsScreen.tsx b/frontend/src/screens/SettingsScreen.tsx
index 95c4578..2ea58e1 100644
--- a/frontend/src/screens/SettingsScreen.tsx
+++ b/frontend/src/screens/SettingsScreen.tsx
@@ -105,8 +105,12 @@ export function SettingsScreen() {
                 <option value="light">Light</option>
                 <option value="dark">Dark</option>
                 <option value="system">System</option>
+                <option value="neon">Neon</option>
               </select>
-              <p className="hint">“System” follows your desktop's light or dark preference.</p>
+              <p className="hint">
+                “System” follows your desktop's light or dark preference. “Neon” is a pure-black
+                theme with pink and purple accents.
+              </p>
             </div>
           </div>
         </section>
diff --git a/frontend/src/state/AppProvider.tsx b/frontend/src/state/AppProvider.tsx
index 0b5541d..6167031 100644
--- a/frontend/src/state/AppProvider.tsx
+++ b/frontend/src/state/AppProvider.tsx
@@ -337,6 +337,10 @@ export function useApp(): AppContextValue {
 
 /** Apply the requested theme (respecting system preference for `system`). */
 export function applyTheme(theme: Theme): void {
+  if (theme === 'neon') {
+    document.documentElement.dataset.theme = 'neon';
+    return;
+  }
   const prefersDark =
     theme === 'dark' ||
     (theme === 'system' && window.matchMedia('(prefers-color-scheme: dark)').matches);
diff --git a/frontend/src/styles.css b/frontend/src/styles.css
index 06e610c..61bdf7d 100644
--- a/frontend/src/styles.css
+++ b/frontend/src/styles.css
@@ -58,6 +58,35 @@
   --shadow-modal: 0 12px 40px rgba(0, 0, 0, 0.6);
 }
 
+/* "Neon" — pure-black Matrix/Cyberpunk palette inspired by the CAJAFUERTE
+   Obsidian theme (MIT): black panels, deep-pink primary (#ff1493), purple
+   secondary (#8b00ff family), yellow highlights (#ffd700). */
+:root[data-theme='neon'] {
+  --bg: #000000;
+  --surface: #0b0b0e;
+  --surface-2: #131318;
+  --surface-hover: #191921;
+  --border: #2b1224;
+  --border-strong: #4d1c3d;
+  --text: #f5f2f7;
+  --text-muted: #a89bb0;
+  --primary: #ff1493;
+  --primary-hover: #ff4fb0;
+  --primary-soft: #2b0a1e;
+  --on-primary: #ffffff;
+  --danger: #ff3355;
+  --danger-soft: #330810;
+  --warning: #ffd700;
+  --warning-soft: #332b03;
+  --success: #00e68a;
+  --success-soft: #04301f;
+  --info: #b388ff;
+  --info-soft: #1c1035;
+  --focus: #ff1493;
+  --shadow: 0 1px 2px rgba(0, 0, 0, 0.6), 0 8px 24px rgba(255, 20, 147, 0.07);
+  --shadow-modal: 0 12px 40px rgba(0, 0, 0, 0.85), 0 0 32px rgba(255, 20, 147, 0.12);
+}
+
 * {
   box-sizing: border-box;
 }
@@ -312,7 +341,8 @@ a {
 
 /* The artwork is black-on-white; flip it in dark themes so it stays black
    bird on dark tile instead of a glaring white square. */
-html[data-theme='dark'] .sidebar-logo img {
+html[data-theme='dark'] .sidebar-logo img,
+html[data-theme='neon'] .sidebar-logo img {
   filter: invert(1);
 }
 
diff --git a/frontend/src/test/SettingsScreen.test.tsx b/frontend/src/test/SettingsScreen.test.tsx
index e88e83d..68ecbf2 100644
--- a/frontend/src/test/SettingsScreen.test.tsx
+++ b/frontend/src/test/SettingsScreen.test.tsx
@@ -29,6 +29,19 @@ describe('SettingsScreen', () => {
     expect(document.documentElement.dataset.theme).toBe('dark');
   });
 
+  it('applies the neon theme to the document', async () => {
+    const backend = createFakeBackend();
+    installFakeBackend(backend);
+    renderWithApp(<SettingsScreen />);
+
+    const themeSelect = await screen.findByLabelText('Theme');
+    fireEvent.change(themeSelect, { target: { value: 'neon' } });
+    await waitFor(() => {
+      expect(backend.state.settings.theme).toBe('neon');
+    });
+    expect(document.documentElement.dataset.theme).toBe('neon');
+  });
+
   it('toggles publish confirmation and npub shortening', async () => {
     const backend = createFakeBackend();
     installFakeBackend(backend);
diff --git a/src/main.rs b/src/main.rs
index 8c74756..6f630a7 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -35,7 +35,7 @@ Commands:
   relays disable <url>            Disable a relay
   relays test <url>               Test a relay connection
   settings get                    Show application settings
-  settings set theme <light|dark|system>
+  settings set theme <light|dark|system|neon>
   settings set confirm <true|false>
   settings set shorten <true|false>
   delete-profile <npub>           Delete a profile (moves it to undo stack)
@@ -442,7 +442,7 @@ fn cli_settings(args: &[String]) -> Result<String, AppError> {
             match key.as_str() {
                 "theme" => {
                     let theme = Theme::parse(value).ok_or_else(|| {
-                        AppError::config("Theme must be one of: light, dark, system")
+                        AppError::config("Theme must be one of: light, dark, system, neon")
                     })?;
                     app.settings.theme = theme;
                 }
diff --git a/src/settings.rs b/src/settings.rs
index 8cddc71..55ee740 100644
--- a/src/settings.rs
+++ b/src/settings.rs
@@ -23,6 +23,7 @@ pub enum Theme {
     Light,
     Dark,
     System,
+    Neon,
 }
 
 impl Theme {
@@ -32,6 +33,7 @@ impl Theme {
             "light" => Some(Self::Light),
             "dark" => Some(Self::Dark),
             "system" => Some(Self::System),
+            "neon" => Some(Self::Neon),
             _ => None,
         }
     }