Clyde Apperson (born 1955) was arrested in 2000 for running the largest illicit LSD manufacturing operation in United States history with partner William Leonard Pickard. The Drug Enforcement Administration claims that Pickard and Apperson produced over 95% of the LSD sold in the United States, and much of the LSD sold in Europe.

In 2003, Apperson was sentenced to 30 years' imprisonment without the possibility of parole.