Oberleutnant Stefan Kirmaier (28 July 1889 – 22 November 1916) was a World War I German flying ace credited with eleven aerial victories.

Kirmaier would succeed Oswald Boelcke as commander of the famed Jagdstaffel 2 before being killed in action.

He was then attached to Kampfeinsitzerkommando (Combat Single-Seater Command) Jametz, and scored his first three victories during July 1916 while flying a Fokker Eindekker.

On 28 October 1916, Boelcke was killed in action, and Kirmaier was entrusted with command of the squadron.

On 22 November, Kirmaier died in action from a bullet through the head fired by either John Oliver Andrews or Kelvin Crawford.