Pretty cool moment from Ellen DeGeneres -- when she hooked up Cincinnati Bengals player Devon Still with a $10,000 DONATION to help his 4-year-old daughter in her fight against cancer.

Still's story has captivated the nation -- his daughter Leah was diagnosed with Neuroblastoma stage 4 cancer in June, and doctors have told her father she has about a 50% chance of survival. Still says she's fighting like hell.

The Bengals announced proceeds of his #75 jersey sales would be used to help raise awareness for pediatric cancer research ... and so far, more than $1 million has been raised.

But Ellen wasn't just wearing his jersey when Still appeared on her show Friday -- she also hooked the NFL player up with a $10k donation to Children's Hospital of Philadelphia ... where his daughter Leah is being treated.

There's more ... Ellen also said she'll be getting celebs to sign her jersey which she plans to auction off to raise even more money for Leah's fight.