Frank Thomson 'Tom' Leighton (born 1956) is an American mathematician and computer scientist renowned for his contributions to theoretical computer science, particularly in parallel algorithms, cryptography, and distributed systems. He earned a bachelor's degree in mathematics from Harvard University in 1978 and a PhD in applied mathematics from Princeton University in 1982. Leighton joined the faculty of the Massachusetts Institute of Technology (MIT) in 1982, becoming a full professor of applied mathematics in 1989 and a member of the Computer Science and Artificial Intelligence Laboratory (CSAIL). His academic work includes authoring influential textbooks and research on topics like the Leighton-Rao algorithm for network optimization, earning him prestigious awards including the Nevanlinna Prize in 1997.

In 1998, Leighton co-founded Akamai Technologies with Daniel Lewin, pioneering content delivery network (CDN) technology. Initially serving as Chief Scientist and CTO, he became CEO in 2004 and has served as CEO since, including his current role as CEO since 2020, while also holding the position of Chief Technology Officer. He oversees the company's major cybersecurity and CDN operations, leading its expansion into cybersecurity, edge computing, and cloud services. Under his leadership, Akamai has grown into a global leader in digital experience protection with a market capitalization exceeding $10 billion, playing a pivotal role in enhancing online performance and security, including defenses against DDoS attacks.

Leighton remains active in academia, teaching at MIT and serving on advisory boards for organizations like the National Science Foundation. His influence extends to policy and industry networks, where he has testified before congressional committees, consulted on cybersecurity matters, and engaged with institutions like the National Academy of Engineering, of which he is a member. His career exemplifies the intersection of theoretical research and practical innovation, influencing modern internet infrastructure, though his work has intersected with legal contexts involving competitors like Cloudflare, Inc. He holds several patents in networking and security.