4 August] 1874 – 16 July 1943) was a Russian and Soviet physician and revolutionary, the younger brother of Aleksandr Ulyanov and Vladimir Lenin.

As a medical student at Lomonosov Moscow State University, he became involved with revolutionary activity and joined the illegal Marxist Rabochiy soyuz ("Workers' Union").

He served as a medical officer in Sevastopol, in Odessa, and on the Romanian front, continuing his revolutionary activities on the side.

[2][3] Ulyanov remained in Ukraine during the aftermath of the October Revolution and the Civil War, working to strengthen the party apparatus in Crimea and was chairman of the short-lived Crimean Socialist Soviet Republic.

During the 1930s, he collaborated with his sister Maria (who was named after their mother) to write reminiscences about their famous brother, Vladimir Lenin, which were published in serial form.