NBA Star Joe Johnson -- Jeweler Billed Me $260k For Crap I Never Bought!

Brooklyn Nets guard Joe Johnson insists ... he's no jewel thief -- and now, he's lashing back against a lawsuit that says he stole $125,000 worth of bling from an Atlanta diamond dealer.

Aydin & Company filed a lawsuit against Johnson earlier this month, claiming the NBA star entered into a purchase agreement back in October 2010 for $125,500 worth of jewelry.

The items in question -- a white gold watch with diamonds, diamond beaded bracelet, black diamond stud earrings and a white gold bezel set rosary.

According to the suit, Johnson took the swag, but never foot the bill -- so Aydin's suing for the price of the jewelry PLUS legal fees, PLUS interest (which grows at a monthly rate of 2%) ... for a grand total of $266,333.05.

But sources close to Johnson tell TMZ ... the lawsuit is total B.S -- explaining, the owner of the store asked Johnson to wear the items on loan and allowed him to return them when he was done.

But when Johnson tried to give the items back, we're told the jeweler refused and slapped him with the bill instead.

Sources tell us, Johnson NEVER agreed to purchase the items and has since tried to return them on numerous occasions -- but no cigar.