SRI International (SRI; originally the Stanford Research Institute) is a nonprofit scientific research institute and organization headquartered in Menlo Park, California, United States. It was established in 1946 by trustees of Stanford University to serve as a center of innovation to support economic development in the region.

The organization was founded as the Stanford Research Institute in 1946, formally separated from Stanford University in 1970, and became known as SRI International in 1977. SRI performs client-sponsored research and development for government agencies, commercial businesses, and private foundations. It also licenses its technologies, forms strategic partnerships, sells products, and creates spin-off companies. SRI's headquarters are located near the Stanford University campus.

SRI's annual revenue in 2014 was approximately $540 million, which tripled from 1998 under the leadership of Curtis Carlson. In 1998, the organization was on the verge of bankruptcy when Carlson took over as CEO. Over the next sixteen years with Carlson as CEO, the organizational culture of SRI was transformed. SRI tripled in size, became very profitable, and created many world-changing innovations using the NABC framework. One of its successes was Siri, a personal assistant on iPhone, which was developed by a company SRI created and then sold to Apple. William A. Jeffrey served as SRI's president and CEO from September 2014 to December 2021, and was succeeded as CEO by David Parekh.

SRI employs about 2,100 people. Sarnoff Corporation, a wholly owned subsidiary of SRI since 1988, was fully integrated into SRI on January 3, 2011.

SRI's focus areas include biomedical sciences, chemistry and materials, computing, Earth and space systems, economic development, education and learning, energy and environmental technology, security, national defense, sensing, and devices. SRI has received more than 4,000 patents and patent applications worldwide.

In the 1920s, Stanford University professor Robert E. Swain proposed creating a research institute in the Western United States. Herbert Hoover, then a trustee of Stanford University, was also an early proponent of an institute but became less involved with the project after being elected president of the United States. The development of the institute was delayed by the Great Depression in the 1930s and World War II in the 1940s, with three separate attempts leading to its formation in 1946.

In August 1945, Maurice Nelles, Morlan A. Visel, and Ernest L. Black of Lockheed made the first attempt to create the institute with the formation of the "Pacific Research Foundation" in Los Angeles. A second attempt was made by Henry T. Heald, then president of the Illinois Institute of Technology. In 1945, Heald wrote a report recommending a research institute on the West Coast and a close association with Stanford University with an initial grant of $500,000 (equivalent to $6,887,000 in 2024). A third attempt was made by Fred Terman, Stanford University's dean of engineering. Terman's proposal followed Heald's but focused on faculty and student research more than contract research.

The trustees of Stanford University voted to create the organization in 1946. It was structured so that its goals were aligned with the charter of the university—to advance scientific knowledge and to benefit the public at large, not just the students of Stanford University. The trustees were named as the corporation's general members, and elected SRI's directors (later known as presidents); if the organization were dissolved, its assets would return to Stanford University.