The Briton started in pole position for the 100th time in his career - the first driver to reach three figures - on the Catalunya track in Barcelona and was alongside Max Verstappen into the first corner, where he was overtaken by the Dutchman.
Hamilton then chased for almost the entire race.
After tactical depot stops, he managed - on fresh tires - to chase his rival and walk past with six laps left.
Thus, Hamilton took his 98th victory in his career and extended the lead in the total.
There was a difference of eight points between him and second Verstappen before this weekend's competition.
It was also Hamilton's fifth straight victory in Barcelona and his sixth victory on the track overall. Thus, he touched the legendary Michael Schumacher's record of six victories in Barcelona.