Douglas Bruce Lenat (born 1950) is the CEO of Cycorp, Inc. of Austin, Texas, and has been a prominent researcher in artificial intelligence, especially machine learning (with his AM and Eurisko programs), knowledge representation, blackboard systems, and "ontological engineering" (with his Cyc program at MCC and at Cycorp). He has also worked in military simulations and published a critique of conventional random-mutation Darwinism based on his experience with Eurisko. Lenat was one of the original Fellows of the AAAI.
Lenat's quest, in the Cyc project, is to build the basis of a general artificial intelligence by manually representing knowledge in the formal language, CycL, based on extensions to first-order predicate calculus.
At the University of Pennsylvania, Lenat received his Bachelor's degree in Mathematics and Physics, and his Master's degree in Applied Mathematics in 1972. He received his Ph.D. from Stanford University (published in Knowledge-based systems in artificial intelligence, along with the Ph.D. thesis of Randall Davis, McGraw-Hill, 1982) in 1976. His advisor was Professor Edward Feigenbaum.
In 1976 Lenat started teaching at Carnegie Mellon and commenced his work on Eurisko, but returned to Stanford in a teaching role in 1978. His continuing work on Eurisko led to attention in 1982 from DARPA and MCC in Austin, Texas. In 1984 he left Stanford to commence work on Cyc, the fruits of which were spun out of MCC into Cycorp in 1994. In 1986, he estimated the effort to complete Cyc would be 250,000 rules and 350 man-years of effort.
- "Intelligence is ten million rules."
- "The time may come when a greatly expanded Cyc will underlie countless software applications. But reaching that goal could easily take another two decades." 
- "Once you have a truly massive amount of information integrated as knowledge, then the human-software system will be superhuman, in the same sense that mankind with writing is superhuman compared to mankind before writing."
- Davis, Randall; Lenat, Douglas B. (1982). Knowledge-Based Systems in Artificial Intelligence. New York: McGraw-Hill International Book Co. ISBN 978-0-07-015557-2.
- Hayes-Roth, Frederick; Waterman, Donald Arthur; Lenat, Douglas B., eds. (1983). Building Expert Systems. Reading, Mass: Addison-Wesley Pub. Co. ISBN 978-0-201-10686-2.
- Lenat, Douglas. "Hal's Legacy: 2001's Computer as Dream and Reality. From 2001 to 2001: Common Sense and the Mind of HAL". Cycorp, Inc. Retrieved 2006-09-26.
- The Editors of Time-Life Books (1986). Understanding Computers: Artificial Intelligence. Amsterdam: Time-Life Books. p. 84. ISBN 0-7054-0915-5.
- Wood, Lamont. Cycorp: The Cost of Common Sense, Technology Review, March 2005
- Douglas Lenat bio page at Cyc.com
- "Beyond the Semantic Web" video lecture at NIPS 2008.
- "How David Beats Goliath" article at The New Yorker.