John Appel Postley (November 29, 1924, Scarsdale, New York – August 1, 2004, Los Angeles, California) was an American entrepreneur. He is recognized as one of the founders of the computer software industry and creator of the first computer software products, Mark IV. Mark IV pioneered the concept and business model of software as a product and became the earliest successful example of that model. In conjunction with Mark IV, Postley was responsible for the creation of the first software users' group, the "IV League", and the first Association for Computing Machinery (ACM) Special Interest Group (SIGBDP, for business data processing).