Vanes Martirosyan -- a stud boxer who just fought Gennady Golovkin last year -- was arrested earlier this month and cops suspect he headbutted his wife.
TMZ Sports has learned 33-year-old Martirosyan -- a middleweight with a career record of 36-4 -- got into an argument with his wife in their Glendale-area home on Sept. 15.
Our law enforcement sources say the altercation started as a verbal fight ... but then things took a violent turn.
We're told the 5-foot-11, 175-pound boxer allegedly grabbed his wife by the arm and is believed to have headbutted her square in the face.