DIRTY dog OWEN WILSON is already cheating on his baby mama!

As The ENQUIRER recently reported, the “Wedding Crashers” star knocked up his 41-year-old married fitness trainer – and now we’ve caught him locking lips with a knockout brunette!

The mystery woman shared an intimate dinner with Wilson and then spent the night at the 44-year-old actor’s home, according to an eyewitness.

Our blockbuster exclu­sive photos show the couple laughing over their meal in our print edition  and then kissing on the street.

“Owen met the woman for dinner on Oct. 8 at a popu­lar Santa Monica restaurant called Rustic Canyon on Wilshire Boulevard,” a pho­tographer who snapped the pair told The ENQUIRER.

“She was already there waiting when Owen arrived.

“They ate dinner, laugh­ing and having a great time, before leaving about 90 minutes later.

“They walked out together, and Owen sud­denly swooped in for an open-mouth kiss. He held her tight while they locked lips for a good 20 seconds.”

The woman climbed into her car, an older Nissan with an out-of-state li­cense plate, and followed Wilson back to his place, said the camera­man.

“She didn’t come out un­til 10 the next morning, eating a banana,” the photographer added.

“Then she drove back to her apartment in Holly­wood.”

The overnight date may shock Owen’s latest baby mama, Swedish-born beau­ty Caroline Lindqvist, who’s expecting his son in January.

As The ENQUIRER re­ported, Caroline is getting a divorce from her hubby, Beverly Hills plastic surgeon Dr. Ritu Chopra, after being separated for over a year.

Owen is already a dad to son Robert Ford Wilson, 2, with ex-girlfriend Jade Duell.

The screen hunk met Caro­line when he hired her as his personal trainer. Caroline now works in real estate in Malibu.

Their friendship evolved into regular sexual romps, said a family friend, and both are reportedly thrilled that they’re expecting a son together.

But, an insider added: “Now that Owen’s had his hands on another woman, Caroline might not want him to be so ‘hands on’ with her!”