Vassian Patrikeyev, also known as Vassian Kosoy (Вассиан Патрикеев, Вассиан Косой in Russian; real name – knyaz Василий Иванович Патрикеев, or Vasili Ivanovich Patrikeyev) (c. 1470 – between 1531 and 1545) was a Russian ecclesiastic and political figure and writer. Patrikeyev traced his male-line descent to Duke Patrikas of Korela and to Gediminas, Grand Duke of Lithuania.
He was known to have been one of the leaders of the boyar party, which supported tsarevich Dmitry Ivanovich (grandson of Ivan III) in a struggle against Sophia Paleologue's son Vasili for succession to the throne.
In ecclesiastic matters, the boyar party was generally closer to heretical and freedom-loving circles.
In 1499, Ivan III found out about the conspiracy against Vasili and ordered arrests (the tsar first favored Dmitry Ivanovich). Vassian Patrikeyev was forced to take monastic vows and sent to Kirillo-Belozersky Monastery.
At the monastery, Patrikeyev became a student of Nil Sorsky and absorbed his philosophy. It appears that in 1503 Patrikeyev and Sorsky came to Moscow to attend a church council (sobor). During this ecclesiastic meeting, the two demanded leniency for the heretics and opposed Joseph Volotsky's views on this issue, subsequently inflaming a dispute between the two parties in the form of personal letters.
During the reign of Vasili III, Patrikeyev reached an important status. Due to his rising influence, many heretics escaped severe punishment. At some point, the tsar even forbade Volotsky to defame Patrikeyev. It appears that Varlaam, who had been close to Nil Sorsky and his followers, was elected Metropolitan bishop with some assistance from Vassian Patrikeyev.