It's the 24th world championship medal for Biles, breaking a tie on 23 with the Belarusian men's gymnast Vitaly Scherbo.
Biles scored 15.066 on the beam after a nearly flawless routine, opting for a simpler dismount than the double-double she performed earlier in the championships.
China took silver and bronze, Liu Tingting getting a 14.433 and Li Shijia a 14.3, respectively.
Biles won the floor exercise by a full point, scoring 15.133 despite a step out of bounds on one pass, and blew kisses to the audience after finishing her routine. U.S. teammate Sunisa Lee took silver, her third medal of the championships, and Angelina Melnikova took bronze for Russia.
Biles has won five events at these world championships after team gold Tuesday, individual all-around gold Thursday and vault gold Saturday.
A fifth place on uneven bars Saturday ended Biles' chances of winning a medal in all six events, which she did last year in her comeback world championships after a sabbatical in 2017.
Of her 24 career world medals, 18 are gold, against 12 of 23 for Scherbo.
Earlier, Russia's Nikita Nagornyy won the men's vault for this third gold medal of the championships. He's the first European man to win the vault since 2010.
Nagornyy scored an average 14.966 from his two vaults, beating his friend and Russian teammate Artur Dalaloyan into second place. The bronze went to Ukraine's Igor Radivilov.
The 38-year-old Romanian Marian Dragulescu, a four-time world champion, secured qualification for his fifth Olympics by placing fourth.