Armen Leonovich Takhtajan or Takhtajian (Armenian: Արմեն Լևոնի Թախտաջյան; Russian: Армен Леонович Тахтаджян; surname also transliterated Takhtadjan, Takhtadzhi︠a︡n or Takhtadzhian, pronounced takh-tuh-JAHN; 10 June 1910 – 13 November 2009), was a Soviet-Armenian botanist, one of the most important figures in 20th century plant evolution and systematics and biogeography.

Takhtajan was born in Shushi, Russian Empire, present-day disputed Nagorno-Karabakh, on 10 June 1910, to a family of Armenian intellectuals.

His grandfather Meliksan Takhtadzhyan Petrovich had been born in Trabzon, Ottoman Empire and was educated in Italy, on the island of San Lazzaro degli Armeni, an Armenian enclave, spoke many languages and worked as a journalist.

His father, Leon Meliksanovich Takhtadzhyan (1884–1950), was born in Batumi, Georgia and was educated as an agronomist at Leipzig University.

Arriving in Shushi in 1908, then a centre of sheep farming in the Caucasus, looking for work, Leon was forced to teach German at the local Realschule attached to the Armenian seminary, due to lack of opportunities in his chosen field.

There he came under the influence of one of his teachers, Alexander Konstantinovich Makaev (Makashvili) (1896–1962), who had previously taught agriculture at Tbilisi State University, and had produced a dictionary of botanical names in Georgian, Russian and Latin.

There he volunteered at the biology school at Leningrad University and attended lectures by Vladimir Leontyevich Komarov (1869–1945) on plant morphology.

(Takhtajan, Crovello and Cronquist, 1986) For many years restrictions were placed on his work because of his opposition to the official line on genetics promoted by Lysenko.

[11] In 1980, botanist Vandika Ervandovna Avetisyan published Takhtajaniella, which is a genus of flowering plant from Transcausica, belonging to the family Brassicaceae and it was named in his honour.