Boris of Tver or Boris the Great (ca. 1399–February 10 1461) was a prince of Tver.

Boris, the son of Alexander II of Tver, was Grand Prince of Tver

Grand Prince of Tver

The title of Prince of Tver was borne by the head of the branch of the Rurikid dynasty that ruled the Principality of Tver. In 1247 Tver was allocated to Grand Prince Alexander Nevsky, and became an independent principality...

 from April 22 1426 to his death. He first married to Anastasia Andreevna of Mozhaysk

Mozhaysk

Mozhaysk is a town and the administrative center of Mozhaysky District of Moscow Oblast, Russia, located to the west from the Russian capital, on the historic road leading to Smolensk and then to Poland. Population:...

 and had a daughter Maria of Tver

Maria of Tver

Maria Borisovna of Tver was the first wife of Grand Prince Ivan III and daughter of Boris Alexandrovich of Tver....

 (future wife of Ivan III of Moscow), second to Anastasia Alexandrovna of Suzdal

Suzdal

Suzdal is a town in Vladimir Oblast, Russia, situated northeast of Moscow, from the city of Vladimir, on the Kamenka River. Population: -History:...

, and had two sons - Mikhail III of Tver

Mikhail III of Tver

Mikhail III of Tver or Michael the Exile was the last prince of Tver.Mikhail was the son of Boris of Tver and Anastasia of Suzdal . He was Grand Prince of Tver from February 10 1461 to 1485...

 and Alexander.
During his reign, the story of Third Rome

Third Rome

The term Third Rome describes the idea that some European city, state, or country is the successor to the legacy of the Roman Empire and its successor state, the Byzantine Empire ....

("the second Constantine") started in Tver, when the monk Foma (Thomas) of Tver had written The Eulogy of the Pious Grand Prince Boris Alexandrovich in 1453.