False Dmitry I or Pseudo-Demetrius I (Russian: Лжедмитрий I, romanized: Lzhedmitriy I) reigned as the Tsar of all Russia from 10 June 1605 until his death on 17 May 1606 under the name of Dmitriy Ivanovich (Russian: Дмитрий Иванович). According to historian Chester S. L. Dunning, Dmitry was "the only Tsar ever raised to the throne by means of a military campaign and popular uprisings".
He was the first, and most successful, of three impostors who claimed during the Time of Troubles to be the youngest son of Ivan the Terrible, tsarevich Dmitry Ivanovich, who supposedly escaped a 1591 assassination attempt when he was eight years old. It is generally believed that the real Dmitry of Uglich died in Uglich in 1591. False Dmitry claimed that his mother, Maria Nagaya, anticipated the assassination attempt ordered by Boris Godunov and helped him escape to a monastery in the Tsardom of Russia, and the assassins killed somebody else instead. He said he fled to the Polish–Lithuanian Commonwealth after he came to the attention of Boris Godunov, who ordered him seized. Many Polish nobles did not believe his story, but nonetheless supported him.