Two of John Mayer’s famous ex-girlfriends face off

Drake celebrated his 30th birthday at LA hotspot Delilah on Sunday with starry guests including “Bad Blood” exes Taylor Swift and John Mayer.

“The tension was so thick, you could cut it with a knife,” a spy told us.

Mayer’s other ex Katy Perry also attended, and sources told us she and Swift completely avoided each other.

“They were put on opposite sides of the room and didn’t even look at each other. Taylor came through the front door with Karlie Kloss and the Haim sisters while Perry entered through the back with a gang of friends, who were inappropriately dressed for the formal affair. Katy and John chatted, but Taylor avoided both of them,” a spy said.

Guests noshed on dinner from Carbone and sipped Virginia Black whiskey cocktails.

We’re told after the dinner, Drake joined Swift in her booth, where they “were intimately flirting, talking closely and laughing. The only person he spent more time with other than his mom was Taylor,” the source said.

Funnyman Jamie Foxx grabbed the mic and jokingly asked Mayer if he had his guitar to come up and do a song. Mayer did not sing.

Reps for Swift and Drake did not comment.