NBA Star Joe Johnson -- I Want My Baby to Inherit My MASSIVE NBA Contract

Brooklyn Nets guard Joe Johnson has a $126-million contract tied to his name and now he's filed legal docs to make sure his son gets a piece of it ... TMZ has learned.

The All-Star guard filed paternity paperwork earlier this week in Georgia to legally establish himself as the father of his alleged 5-year old son, whose mother is named Shannon Beckton.

In the docs, Johnson says he still wants to test for DNA (just in case) ... but if he is the father, he is asking the judge for joint physical and legal custody, for his son to be able to inherit from him, and for his son to take on his last name.