Harold Abelson, often referred to as Hal Abelson, is a notable American mathematician and computer scientist, born on April 26, 1947. He is a professor of computer science and engineering at the Massachusetts Institute of Technology (MIT) in the Department of Electrical Engineering and Computer Science.

Abelson is a founding director of both Creative Commons and the Free Software Foundation. He is the creator of the MIT App Inventor platform and co-author of the widely used textbook Structure and Interpretation of Computer Programs (SICP), also known as 'the wizard book' due to its distinctive cover illustration.

He directed the first implementation of the language Logo for the Apple II, making it widely available on personal computers starting in 1981, and published a popular book on Logo in 1982. In collaboration with Gerald Jay Sussman, Abelson developed MIT's introductory computer science subject, "The Structure and Interpretation of Computer Programs," organized around the concept that a computer language is a formal medium for expressing ideas about methodology.

Additionally, Abelson and Sussman are co-directors of the MIT Project on Mathematics and Computation. Abelson played a pivotal role in the MIT OpenCourseWare (OCW) project, alongside other MIT faculty. He also led an internal investigation into MIT's involvement in the prosecution of Aaron Swartz by the FBI, which concluded with recommendations for policy changes at MIT.