Nikki Bella and Cooper DeJean have whipped up speculation that something is going on between them ... and TMZ has learned there's for sure a spark.

A source with knowledge tells TMZ ... the WWE star and Philadelphia Eagles cornerback have been spending some time together and even been on dates ... but Nikki is still very single and enjoying life.

We hear there's definitely a mutual attraction there -- but again, it's casual -- and NB's primary focus is on her career and raising her son, Matteo.

The rumors have been swirling for a few weeks that something might be going on between the two after Nikki went to a couple of Eagles games ... rockin' Cooper's jersey!

And while it's just some dates ... this is a pretty big step for Nikki, whose rocky divorce from Artem Chigvintsev in 2024 made a whole lotta headlines. But, Nikki has since said on her podcast, "The Nikki and Brie Show," she and Artem are in a good place and are co-parenting.

We reached out to a rep for Nikki for comment ... so far, no word back.