UFC's Dan Henderson: This 'Old Man' Is Gonna Beat Bisping's Ass!

UFC superstar Dan Henderson says Michael Bisping can crack all the geriatric jokes he wants -- 'cause when the two face off in the Octagon, Bisping's gonna "end up getting his ass beat by an old man."

45-year-old Dan joined the guys on the "TMZ Sports" TV show -- and responded to Bisping's trash talk .. specifically when he said he wants to fight Dan before he dies of old age.

It's pretty good stuff ... Dan vows to whoop that ass -- AGAIN -- and says he'll retire right after he does.

He also gives us an update on the contract situation for the fight.

Check out the whole interview tonight on "TMZ Sports" on FS1.