Bristol Palin's new baby daddy may no longer be a mystery ... her ex-fiance says he's the daddy, and he's gunning for some serious custody.
Dakota Meyer filed legal docs, obtained by TMZ, in which he claims he's the biological father of 3-week-old Sailor.
Dakota wants a judge to award him joint legal and physical custody.
Bristol has never publicly revealed the identity of the father. She and Dakota broke up 3 months after conception.
Bristol's baby daddy wants one more thing ... child support.