ESPN.com confirmed the 185-pound matchup with UFC officials, following an initial report from Brazilian news site Combate. The pay-per-view event will take place at HSBC Arena.
Gastelum (14-2), 25, specifically asked for the matchup last weekend, after he scored a first-round knockout over Vitor Belfort in Fortaleza, Brazil. It marked Gastelum's third consecutive win.
The Brazilian legend celebrates his 42nd birthday next month and is coming off a controversial decision win over Derek Brunson at UFC 208 in February. It was Silva's first official win since 2012.
The UFC has not yet announced whether the Silva-Gastelum fight will serve as the co-main event. A featherweight unification bout between Jose Aldo (26-2) and interim champion Max Holloway (17-3) will headline the card.