Gilbert Arenas says the restraining order a woman got against him was based off straight-up manufactured bulls**t that cost him a boatload of money … and he’s fighting back in court.

Here’s the deal … a woman named Janelle Reeves — who claims she dated Arenas — got a restraining order against the NBA star in June.

Reeves claims Arenas took the breakup hard … and harassed and tormented her — and threatened to send explicit videos of her to her son.

The restraining order was eventually dismissed by the judge after Reeves was a no-show for court.

But, Arenas just ain’t letting it go … he’s now filed a lawsuit against the woman claiming she fabricated the whole thing.

[more at tmz.com]