Travis Kelce might've been without Taylor Swift this weekend while raging with his teammates in Las Vegas (again) -- but he certainly had her on his mind ... take a look.

Videos of the NFL star belting out "Love Story" at XS nightclub at the Wynn are circulating all over social media -- and considering his enthusiasm over a T-Swift classic, it's safe to say she was sorely missed for the good time he and the Chiefs were having here.

These clips capture just a snapshot of Travis' rager ... and he wasn't just singing Taylor tracks -- dude was out there screaming his lungs out to a ton of other tunes, celebratory and otherwise.

There's been a little criticism that TK surrounded himself with a bunch of hot women during his night out in Vegas with the boys -- but clearly ... Tay Tay is front and center in his heart.

As for the rest of the celebration ... well, we covered it pretty well already. He was enjoying himself next to Patrick Mahomes and just about every other Chiefs player who helped the team win the Super Bowl a few weeks ago ... with everyone coming back for round 2.

Travis was only in Sydney for a couple days with Taylor before he hightailed it out of there and flew back to Vegas for yet another victory lap with the guys ... and they partied hard.

Taylor, meanwhile, was busy finishing out the rest of her Australia stint -- and soon, she'll be flying off to Singapore for more shows. Unclear if Travis is tagging along for that or not.