László "Les" Bélády (born April 29, 1928 in Budapest) is a Hungarian computer scientist notable for devising the Bélády's Min theoretical memory caching algorithm in 1966 while working at IBM Research. He also demonstrated the existence of a Bélády's anomaly. During the 1980s he was the editor-in-chief of the IEEE Transactions on Software Engineering.
Bélády earned B.S. in Mechanical Engineering, then an M.S. in Aeronautical Engineering at the Technical University of Budapest. He left Hungary after the Hungarian Revolution of 1956. He worked as a draftsman at Ford Motor Company in Cologne and as an aerodynamics engineer at Dassault in Paris. In 1961 he immigrated to the United States, where he joined International Business Machines and did early work in operating systems, virtual machine architectures, program behavior modeling, memory management, computer graphics, Asian character sets, and data security. In the 60s and 70s he primarily lived in New York City with stints in California and England.
In his later years at IBM he was responsible for software engineering worldwide until leaving for Tokyo to create its software research lab. He retired from IBM two years later. In 1984 he joined the Microelectronics and Computer Technology Corporation in Austin and founded its Software Technology Program. He focused the program on creating advanced technology for aiding the distributed design of large complex software systems. From 1991 to 1998 he served as President and CEO of Mitsubishi Electric Research Laboratories, Inc. (MERL). He has been in various University advisory roles including a member of the computer science advisory board at the University of Colorado at Boulder. He is now retired spending much of his time in Budapest and Austin.