John Kaplan (1929 – November 25, 1989) was a legal scholar, social scientist, social justice advocate, popular law professor, and author. He was a leading authority in the field of criminal law, and was widely known for his legal analyses of some of the deepest social problems in the United States. He was known for his work linking sociological research with legal policies, and limiting academic legal theory with real-world sociological data. He was an advocate for ending criminal prohibitions on private behavior such as drug use, arguing that these laws only made any problems worse.