USC head football coach Steve Sarkisian had a bad 4/20 ... his marriage went up in smoke.
TMZ Sports has obtained court docs, filed in L.A County Superior Court, which show Steve's wife, Stephanie, filed for divorce on April 20th -- citing irreconcilable differences.
The two have been married since 1997. They have 3 young children together.
The couple issued a joint statement about the split a few days ago saying, "It is our desire to protect the privacy of our children and each other."
"Our goal is to raise our children in a joint, cooperative style as caring and loving parents."