Bill Nye the Science Guy is dragging his ex-girlfriend back to court -- claiming she forced him to rack up $57,000 in attorney's fees by acting like a crazy stalker ... and is now refusing to pay the bill.

According to the docs, it all started back in 2006 after the couple broke up -- Bill claims his ex Blair Tindall stole several expensive items from his house, including his laptop, which she then used to send defamatory emails impersonating him. Bill claims she also poured herbicide on his rose bushes.

TMZ broke the story back in 2007 ... Bill sought out a protective order as a result -- and obtained a 6-year injunction against her a few months later, requiring her to stay 100 yards away from him.

According to the new docs, Tindall violated that order in 2009 -- so he went back to court to enforce it ... and racked up a $57,000 legal bill in the process. The court then ordered Blair to cover the damage.

Bill claims she hasn't forked over a penny since -- so now, he's dragging her back to court to get his money.

Blair tells TMZ ... "Bill Nye was the love of my life. I'm surprised he has taken this action against me.  I have no funds to pay him, and he is a very wealthy man, so I'm not sure where this is coming from."