Katy Perry and Justin Trudeau Make Out in Santa Barbara

Katy Perry and Justin Trudeau may be grown, but they're living the teenage dream ... making out in the grass like a couple of lovebirds ... and we've got the photos!!!

The couple got cute and cozy during a picnic in Santa Barbara over the weekend, packing on the PDA while they laid out on a blanket.

Katy and Justin rolled up in the pop star's Moke with some food for a sweet park picnic ... and they even brought a couple of kids along for a little family fun.

The "Legendary Lovers" singer and the former prime minister of Canada got some quick kisses in whenever they had a second to themselves, locking lips a few times.

Katy and Justin both kept it casual for their outdoor outing ... Katy wore a white T-shirt, striped pants and a sun hat, while JT donned a green tee, dark shorts and some shades.

They each wore flip-flops, which they could easily kick off to get horizontal on the grass.