Steven Tyler Scores Legal Win In Sex Assault of Minor Lawsuit

Huge legal win for Steven Tyler ... the woman suing him for allegedly sexually assaulting her over 50 years ago when she was 16 years old just had her lawsuit against him whittled down significantly.

Julia Holcomb is suing the legendary Aerosmith frontman over a years-long relationship back in the day ... she filed her lawsuit in California and included a bunch of claims about sexual encounters in various states ... but now a judge has ruled only one claim from an alleged incident in California can remain as the case moves forward ... according to new legal docs obtained by TMZ. The judge ruled the alleged instances of sex in other states -- such as Massachusetts and Oregon -- cannot move forward in a California court.

Steven's attorney, David Long-Daniels, tells TMZ ... "This is a massive win for Steven Tyler. Today, the court has dismissed with prejudice 99.9% of the claims against Mr. Tyler in this case. The court has decided that only one night fifty-plus years ago out of a three-year relationship is allowed to remain. We look forward to trying this case on August 31."

The one claim that remains in Julia's lawsuit is an allegation that she and Steven had sex in a hotel and public hot tub on a visit to California in 1974 when she was 16 years old.

It's worth noting ... Julia and Steven were still living together a year later in June 1975, and were engaged and expecting a child.