The New Zealand singer kicked off her North American tour in Milwaukee on Thursday night (March 1).
During the gig, she covered Ocean’s ‘Blonde’ cut ‘Solo’ and played an unheard number.
Watch footage of both performances beneath.
Tabloid reports have linked the pair romantically following Antonoff’s recent split from long-term girlfriend Lena Dunham.
Speaking to fans in an Instagram Live video, Lorde said: “Guys: Never. No. Jack and I are not dating. For the last time.”
“I love him, he’s awesome,” she added. “But we’re not dating. Please!”
Last month saw Lorde win the Best International Solo Artist prize at the VO5 NME Awards 2018. She couldn’t attend the ceremony, but you can see the message she sent in the clip above.