The Briton, who levelled the record at the Eifel Grand Prix earlier this month, extended his lead over Mercedes teammate Valtteri Bottas, who finished second in Portimao, in the world championship.
Hamilton would level another Schumacher record with a seventh world title this season. It was his eighth win of the season from just 12 races in 2020, with only five remaining in the coronavirus-truncated campaign.
Dutchman Max Verstappen completed the podium for Red Bull, while Charles Leclerc produced a brilliant drive to finish fourth for Ferrari.
It was the seventh race this year that Hamilton, Bottas and Verstappen have made up the top three.