The singer and rapper tweeted Friday afternoon, "Hi guys. I wanted you to hear it from me first. Unfortunately I have to have surgery on my tonsils asap. The surgery is routine but the recovery is going to take awhile [sic] due to swelling. That means I have to cancel my festival run this summer as well as The Weeknd tour. I feel horrible about this but can't wait for this to heal and get back to making music and create and experience for y'all."
Doja Cat had been set to headline Lollapalooza Sunday night along with Green Day. The festival's official account replied to her tweet, writing, "We are saddened by the cancellation of @DojaCat's summer tour, including her headlining set at #Lolla. We wish her a speedy recovery. A replacement will be announced soon."
Doja Cat recently won four Billboard Music Awards, including top R&B artist and R&B female artist for the second consecutive year, along with top R&B album and female artist.
Lollapalooza will be held July 28 through 31 in Grant Park. Other headliners include Metallica, Dua Lipa, J. Cole, Green Day, Machine Gun Kelly, Lil Baby and Kygo.
You can buy tickets here.
The Associated Press contributed to this report.