Leonard Irving Weinglass (August 27, 1933 – March 23, 2011) was a U.S. criminal defense lawyer and constitutional law advocate, best known for his defense of participants in the 1960s counterculture. He was admitted to the bar in New Jersey, New York, Connecticut and California. He taught criminal trial advocacy at the University of Southern California Law School from 1974 to 1976, and at the Peoples College of Law, in Los Angeles, California from 1974 to 1975.