Khaiser Dzhemilev, the son of Crimean Tatar leader Mustafa Dzhemilev, was released from a penal colony in Astrakhan in southern Russia on November 25.
Dzhemilev's lawyer, Nikolai Polozov, said in a Facebook post on November 26 that Dzhemilev has arrived in Ukraine.
Dzhemilev was granted early release from a three-and-a-half year sentence on manslaughter and weapons possession charges.
Dzhemilev was initially convicted by a Ukrainian court in 2013 of accidentally shooting one of the family's bodyguards, Fevzi Edimov.
After Russia's annexation of Crimea in March 2014, the Moscow-backed authorities took over the case, moved him to mainland Russia and tried him again on the same charges.
Mustafa Dzhemilev, who strongly protested the annexation of Crimea and is currently living in Kyiv, said that Russia was using his son to blackmail him into stopping his campaign against the annexation.
Dzhemilev, 72, has been banned from Crimea since Russia invaded and annexed the peninsula in early 2014.
He had been the chairman of the Crimean Tatars' Mejlis, or council, until it was banned by pro-Moscow representatives in Crimea.
He is a member of the Ukrainian parliament and a well-known Soviet-era human rights activist.