The fights will be broadcast on ESPN, ESPN Deportes and ESPN+, with the main card starting at 10 p.m. ET and the prelims at 7 p.m.
Whittaker (22-5) has won 11 of his past 12 fights, the lone loss coming on the night in 2019 when Israel Adesanya took away his title by knockout. In his most recent fight, in October, Whittaker defeated Jared Cannonier by unanimous decision. Whittaker is No. 2 in the ESPN middleweight rankings.
Gastelum (16-6, 1 NC) is coming off a unanimous decision win over Ian Heinisch in February, which ended a three-fight losing streak. That skid began with a 2019 loss to Adesanya in an interim title fight.
There's also another intriguing heavyweight bout on the undercard, featuring Alexander Romanov, a Moldovan who is 13-0 with finishes in every fight -- 10 of which have come in the first round. He faces Spaniard Juan Espino, who has won eight in a row, with six of those wins coming by first-round finish.
How to watch the fights
Watch the entire card on ESPN. Don't have ESPN? Get instant access.
All of the fights are also available on ESPN Deportes and ESPN+. ESPN Deportes is available at the same link above for ESPN. If you don't have ESPN+, get it here. Also: Download the ESPN App | WatchESPN | TV schedule
There's also FightCenter, which offers live updates for every UFC card.
Saturday's fight card
ESPN/ESPN Deportes/ESPN+, 10 p.m. ET
Robert Whittaker vs. Kelvin Gastelum | Middleweight
Jeremy Stephens vs. Drakkar Klose } Lightweight
Andrei Arlovski vs. Chase Sherman | Heavyweight
Abdul Razak Alhassan vs. Jacob Malkoun | Middleweight
Luis Peña vs. Alexander Muñoz | Lightweight
ESPN/ESPN Deportes/ESPN+, 7 p.m. ET
Tracy Cortez vs. Justine Kish | Women's flyweight
Alexander Romanov vs. Juan Espino | Heavyweight
Jessica Penne vs. Lupita Godinez | Strawweight
Gerald Meerschaert vs. Bartosz Fabiński | Middleweight
Austin Hubbard vs. Dakota Bush | lightweight
Tony Gravely vs. Anthony Birchak | Men's bantamweight