Putin, 65, has been in power, either as president or prime minister, since 2000, longer than veteran Soviet leader Leonid Brezhnev and outstripped only by dictator Josef Stalin.
If he wins what would be a fourth presidential term, he will be eligible to serve another six years until 2024, when he turns 72.
Backed by state TV, Putin regularly enjoys approval ratings of around 80 percent, and his decision to run for re-election -- which he announced at a car-making factory in the Volga river city of Nizhny Novgorod -- was widely expected.
Allies laud Putin as a father-of-the-nation figure who has restored national pride and expanded Moscow’s global clout with interventions in Syria and Ukraine.
Critics accuse him of overseeing a corrupt authoritarian system and of illegally annexing Ukraine’s Crimea in 2014, a move that isolated Russia internationally.
Opposition leader Alexei Navalny, who is unlikely to be allowed to run against Putin due to what he says is a trumped up criminal conviction, said Putin was overstaying his welcome.