Aleksandr Antonovich Troyanovsky (Russian: Алекса́ндр Анто́нович Трояно́вский; 13 January [O.S. 1 January] 1882 – 23 June 1955) was a Russian revolutionary, military officer and Soviet diplomat who served as the first authorized Soviet Ambassador to the United States.

Troyanovsky was born in to the family of a hereditary nobleman and brigadier commander in the Imperial Russian Army. His father died from tuberculosis when he was a child. He and his younger brother joined the military and after graduating from the Mikhailovsky Artillery School he was sent to serve in the 33rd artillery brigade of the Kiev Military District.

From 1904 he was a member of the Russian Social Democratic Labour Party's Bolshevik faction and spread revolutionary and anti war propaganda during the Russo-Japanese War.

In April 1905, he was sent to an artillery unit that took part in battles with Japanese troops in Manchuria. He resigned as a lieutenant in 1906, and in 1907 by the decision of the Kiev military district court he was deprived of all the rights of a retired officer.

In 1908 he was arrested for revolutionary activity, and on 24 February 1909 was sentenced by the Kiev District Court to administrative deportation to the Yenisei province. He served exile in the village of Tikhanovo, Belskaya volost, Yenisei district.

In 1910 he escaped from exile and emigrated abroad with forged documents. He collaborated with the Bolsheviks. A member of the 9th Congress of the Second International in 1911 and the Poroninsky meetings of the Central Committee of the RSDLP with other party cadres. He was a member of the foreign editorial board of the journal "Education". He lived in France and Austria during exile, collaborated with V. I. Lenin and met with Joseph Stalin.

He broke with the Bolsheviks in 1914, became a Menshevik and maintained defencist positions.

In 1917 he returned to Russia, joined the Imperial Army, took part in hostilities on the Southwestern Front.