Justin Trudeau was totally vibing as he heard Katy Perry “Roar” at Wednesday’s “Lifetimes” tour!

Several videos posted by fellow concertgoers show the former Canadian Prime Minister with a cautious grin on his face … swaying and completely locked in on KP as she belted out her biggest hits.

We even caught him in a full-teeth smile as he sang along to “Roar” … while the pop star flew over him in her oversized mechanical butterfly — yes, the one that nearly threw her into the crowd a few weeks ago.

Unclear if the pair met up after the show … but as you know, we caught them dining Monday evening at the swanky Le Violon restaurant.

We’re told they’re just pals and there was no PDA to see during their dinner … but they looked slightly more than that as they cozied up on a terrace later on in the evening for some drinks. We’ll let you be the judge here.

Unless you’ve been living under a rock, you’re well aware Katy is currently on her world tour following her seventh studio album, “143.” She kicked it off in Mexico City in April … just a few weeks before we confirmed she and Orlando Bloom called it quits.

The pair had been together for 9 years — which included a 6-year engagement. They also welcomed their daughter, Daisy Dove, in 2020.