EXCLUSIVE

Chad Johnson's wife of 6 weeks has filed for divorce ... TMZ has learned.

Evelyn Lozada filed legal docs moments ago in Florida, claiming her marriage is "irretrievably broken."

The trigger for the divorce was the domestic violence incident over the weekend, in which Chad Johnson was arrested after allegedly head-butting her during an argument.

Evelyn claimed she found a receipt for a box of condoms in his car.

According to the divorce docs, the couple had a prenup -- but that won't be a big deal since the marriage was shorter than Kim Kardashian's.