They went on sale at 10 a.m. Thursday, and sold out in less than an hour.
But, one- and two-day tickets are now on sale and available.
Lolla also revealed the lineup by day.
Tyler, The Creator and Luke Combs are headlining Thursday. Gracie Abrams, Dom Dolla and Cage The Elephant will also perform that day.
Olivia Rodrigo and Korn are on Friday. The Bleachers, T-Pain and Foster The People will also perform Friday.
Rufus Du Sol and Twice are on Saturday, along with Doechii and Two Friends.
Sabrina Carpenter and A$AP Rocky are on Sunday.
Lollapalooza returns to Grant Park July 31 through Aug. 3.
Visit www.lollapalooza.com for more information.