Lionel Cooper Kimerling (born December 2, 1943) is an American materials scientist who studies semiconductor materials and how they are processed. As of 2016, he holds the title of Thomas Lord Professor of Materials Science & Engineering at the Department of Materials Science & Engineering at the Massachusetts Institute of Technology (MIT). From 1981 to 1990, he led the Materials Physics Research Department at AT&T Bell Laboratories.

Kimerling earned his first degree in Metallurgy in 1965 and his Ph.D. in 1968, both from MIT.

His research has focused on silicon microphotonics, the development of the first 1MB DRAM, and the creation of long-lasting telecommunications lasers. His team also developed methods to study semiconductor materials, such as deep-level transient spectroscopy, SEM-electron beam-induced current, and RF-PCD. His work includes silicon processing, which involves creating integrated circuits, microphotonic materials and devices, solar energy conversion systems, and environmentally friendly methods for making integrated circuits. The goal of his microphotonics research is to combine optical connections with microelectronic circuit chips.

In 1987, he was elected a Fellow of the American Physical Society "for fundamental contributions to the measurement and understanding of the electrical properties of defects in semiconductors and the role of charge state and electronic stimulation in their structure and reactivity."

As Thomas Lord Professor of Materials Science and Engineering at MIT, Kimerling helped launch the first global roadmap for integrated photonics: Integrated Photonics Systems Roadmap – International (IPSR-I). This roadmap was created by the MIT Microphotonics Center in the United States and PhotonDelta in Europe, combining their two earlier separate roadmaps, IPSR and WTWF.