By TMZ Sports

Former three division world champion "Sugar" Shane Mosley is being investigated for an alleged domestic violence incident after his girlfriend told police he roughed her up this weekend ... TMZ Sports has learned.

Law enforcement sources confirm cops were called to an L.A. home just after midnight on Sunday morning. When they arrived to the scene, 45-year-old Shane was not there.

The accuser told cops she and Shane had been arguing earlier in the night -- but things escalated and Shane pushed her. The woman claimed she suffered minor injuries and complained of pain. We're told cops are investigating the incident.

Shane tells TMZ Sports he did NOTHING wrong. He says the two had a verbal argument and she "tripped."

He adds, "I didn't push her. She tripped and she didn't have any injuries. We were just yelling."

Mosley (49-10-1, 41 KOs) has been out of the ring since last May, when he lost a twelve round decision to unbeaten WBA interim-welterweight world champion David Avenesyan. The fight was also a final eliminator for a world title crack against WBA champion Keith Thurman.

Mosley, 45-years-old, has technically not announced his retirement and may fight again in the future if the right opportunity comes along.