With almost all the ballots counted, he had received more than 76% of the vote, the central election commission said.
The main opposition leader, Alexei Navalny, was barred from the race.
Addressing a rally in Moscow after the early results were declared, Mr Putin said voters had “recognised the achievements of the last few years”.
Speaking to reporters, he laughed off a question about running again in another six years.
“What you are saying is a bit funny. Do you think that I will stay here until I’m 100 years old? No!” he said.
The scale of victory – which had been widely predicted – appears to be a marked increase in his share of the vote from 2012, when he won 64%.
Mr Putin’s nearest competitor, millionaire communist Pavel Grudinin, received about 12%.
The race also included Ksenia Sobchak, a former reality TV host, and veteran nationalist Vladimir Zhirinovsky – they got less than 2% and about 6% respectively.
A state exit poll put the turnout at over 60%. Mr Putin’s campaign had hoped for a large turnout, to give him the strongest possible mandate.
His campaign team said it was an “incredible victory”.
“The percentage that we have just seen speaks for itself. It’s a mandate which Putin needs for future decisions, and he has a lot of them to make,” a spokesman told Russia’s Interfax.
In some areas, free food and discounts in local shops were on offer near polling stations.
Video recordings from polling stations showed irregularities in a number of towns and cities across Russia. Several showed election officials stuffing boxes with ballot papers.
Mr Navalny was excluded from the election because of an embezzlement conviction that he said was manufactured by the Kremlin.
In his first reaction to the news, Mr Navalny indicated he had been unable to contain his anger.
“Now is the season of Lent. I took it upon myself never to get angry and not to raise my voice. Oh well, I’ll try again next year,” he tweeted.
During polling day, independent election monitoring group Golos reported hundreds of irregularities. (Courtesy BBC)