Taylor Swift, Travis Kelce In Honeymoon Phase at Super Bowl After-Parties

Taylor Swift and Travis Kelce look like a high school couple who have fallen in love for the first time ... at least that's the vibe they put out at Super Bowl after-parties in Las Vegas.

Nitish Kannan, a film producer who partied with Taylor and Travis in Sin City, joined us on "TMZ Live" Monday and painted a picture of what it was like celebrating the Kansas City Chief's big win alongside Hollywood's "it" couple.

Taylor and Travis started the postgame festivities with a private party at Zouk inside Resorts World Las Vegas before moving over to XS at the Wynn ... and when they weren't singing her hit songs to each other, they were making out.

Nitish tells us Tay Tay and TK seemed to be having the times of their lives ... and looking like they're in the honeymoon phase of their relationship.

While the singer and football player commanded the spotlight all night, Nitish says Taylor and Travis wanted to just have a normal night out in public with friends, family and teammates.

It's kinda the exact opposite of Taylor's last relationship -- looking at you, Joe Alwyn -- and that might be one reason why this is all working so well.

Travis, Nitish noticed, isn't very clingy or needy ... and Taylor's very into him. The whole night TK would be hanging with Taylor, then suddenly with his teammates ... and was just generally nice to everyone. That's what Nitish here is saying.