3:40 PM PT -- Jay Glazer ran into Pratt at the gym and congratulated him, and Chris used it as an excuse to show off his wedding ring as well. Pratt also had a very quick but interesting message ... check it out.

2:26 PM PT -- Chris also seems to be in the mood to work out before he and his new bride get into honeymoon mode -- but he's doing so across town from his wife. The actor was spotted Tuesday leaving a WeHo gym, right around the time Kat was doing the same in Brentwood.

Sure, they just got hitched three days ago -- but hey, it's 2019. Do your thing, babe! See ya at home.

Katherine Schwarzenegger's not off on a fabulous honeymoon yet ... but she's still rocking that newlywed smile and GIANT ring while working on her fitness.

Katherine was beaming Tuesday as she left a pilates sesh in Brentwood. We're guessing that ear-to-ear grin has more to do with her husband, Chris Pratt, than working up a sweat ... but ya never know. She IS Arnold's daughter!

As we reported ... the couple tied the knot over the weekend at the ritzy San Ysidro Ranch in Montecito. The event, as you can imagine, was a pretty star-studded affair. Heck, the wedding rehearsal alone was at Rob Lowe's crib!

This is Katherine's first marriage, and Chris' second. He was famously married to Anna Faris, who was so happy for him and Katherine, she volunteered -- jokingly, we think -- to marry them.

That wasn't necessary, as it turned out, and the wedding went off without a hitch.

Congrats ... to Katherine, we mean. Pilates is hard!