Frank Ocean -- My Dad's Suing Russell Simmons ... For $142,000,000

Frank Ocean's father just slapped hip hop mogul Russell Simmons with a $142 million lawsuit for calling him a deadbeat dad.

Calvin Cooksey -- who hasn't been part of Ocean's life since his son was 5 -- says he's been unfairly portrayed as a horrible father on Simmons' website, Global Grind.

In his lawsuit, Cooksey goes on the attack -- saying he wasn't allowed to be a father to Frank because his "Money Grubbing mother" moved, and hid the boy from him.

Cooksey says Simmons published lies about him without checking facts -- and worst of all ... never bothered to use his actual name in the posts about Ocean's father. Translation: at least defame me by using my proper name!

Cooksey is suing for loss of future income -- he describes himself as a singer, writer and inventor -- and thinks the $142 million should just about cover it.