Frank Ocean's dad is suing the hitmaker.

In legal papers obtained by TMZ, Calvin Cooksey claims his son defamed him in a Tumblr post last year (16).

The singer accused his dad of using a homophobic slur when he was a kid, writing: "I was 6 years old when I heard my dad call our transgender waitress a f**got as he dragged me out of a neighborhood diner saying we wouldn't be served because she was dirty."

Ocean's dad insists the tale is bogus and he has suffered financially and professionally as a result of the post.

He's suing Frank for $14.5 million (GBP11.6 million) in damages.

Calvin also sued rap mogul and entrepreneur Russell Simmons in 2014 for claiming he was a deadbeat dad.