Nikolai Köstner (1889–1959) was an Estonian politician, economist, diplomat and academic. He was a member of the Provisional Assembly of the Autonomous Estonian Governorate (1917–19) and the Constituent Assembly of the newly established Republic of Estonia (1919–20); he also served as a minister in Jaan Raamot's Provincial Government (Estonian: Eesti Maavalitsus) in 1917, in the Second and Third Provisional Governments (1918–19), and in Otto Strandman's first Cabinet and Jaan Tõnisson's first Cabinet. He was also part of the Estonian delegation to the 1919 Paris Peace Conference. In later life, he worked as an academic at the University of Tartu and as an adviser to a number of national banks.