Chad Johnson -- History of Domestic Violence

Chad Johnson is no stranger to domestic violence -- TMZ has learned the former NFL star was secretly found guilty of battering a woman in 2000 ... 12 years before he allegedly struck again.

According to court records obtained by TMZ, Johnson was arrested for misdemeanor domestic battery in L.A. on February 7, 2000 ... just before he began playing football for Oregon State University.

Sources close to the case tell us the victim was his GF at the time ... and she told police the football star had slapped her in the face after he accused her of cheating on him.

According to court records, Johnson -- 22 years old at the time -- pled no contest ... and the court found him guilty of domestic battery.

Johnson was sentenced to 3 years probation and ordered to serve 45 days in L.A. County Jail. But Johnson struck a deal with the court which allowed him to avoid jail ... as long as he completed 30 days of graffiti removal work with CalTrans. Johnson was also required to complete a 12 month batterer's counseling program and ordered to stay 100 yards away from the victim.

But Johnson didn't complete his probation requirements in a timely manner ... according to court records, he blew off the hard labor AND the dom. violence program for years.

After a judge tacked on an additional 15 days of graffiti removal, Johnson finally completed his legal obligations in 2002 ... when he was a member of the Cincinnati Bengals.

Now, Johnson finds himself in a similar situation ... having been accused of battering a woman once again ... his wife Evelyn Lozada.

Johnson told police he did nothing wrong this time around. He's expected back in court soon to enter his plea.

We called Johnson's lawyer. He had no comment.