The violent collision occurred shortly after 2:30 a.m. on the eastbound side of the freeway, near Grand Avenue, according to the California Highway Patrol.
News video showed a mangled sedan that had slammed into the back of a stalled big rig in a traffic lane. The driver, later identified as Officer Baldemar Sandoval, was pronounced dead at the scene.
He was on his way home at the time of the crash, LAPD Chief Michel Moore said in a statement.
"Our thoughts and prayers are with the family of Officer Sandoval, his Central Area family and the men and women of the Los Angeles Police Department during this difficult time," Moore said. "May God welcome Baldemar home."
A Sigalert was issued after the crash, and both CHP and LAPD officers responded to the scene.
Sandoval's body was placed on a gurney and covered with an American flag before being placed in a coroner's van.
Several lanes were shut down as crews worked to clear the scene.
The cause of the collision is under investigation.