Miley Cyrus -- Make Out Sesh DENIED ... By Katy Perry

Katy Perry may have famously kissed a girl and liked it ... but Saturday night in L.A. the singer straight up denied Miley Cyrus when she tried slipping Katy the tongue.

Miley's "Bangerz" tour rolled through the Staples Center last night and Katy was front row ... and when Cyrus spotted her she crawled off stage to go in for a smooch.

The look on Miley's face after being shut down is classic.