WOW!!!! Frank Ocean wins Legal Battle against Father.

Frank Ocean's father got his day in court and lost the defamation suit he filed against his son for calling him a bigot.

The singer's dad, Calvin Cooksey, had sued him ... claiming Frank defamed him with a social media post recalling a story from his childhood. Frank said his pop had called a transgender waitress "a f****t."

A judge heard the case in L.A. Tuesday, and ruled in favor of Frank ... saying Cooksey failed to prove his son had defamed him at all. Frank's attorney tells us, "It was a sad case, but we are glad that it ended in Frank's favor and that it is over."