Katy Perry & John Mayer -- Sooooooo Dating

Katy Perry and John Mayer don't need to say it ... they're definitely an item.

The pair have been spotted all over town recently and last night ... our photog caught them coming out of a house party in Los Feliz. Not a lot of recording sessions done at house parties in Los Feliz.

The couple(?) didn't say a word -- and neither has commented publicly on the relationship(?) -- but come on ... we know what's up.