Warren Weaver (b. July 17, 1894 in Reedsburg, Wisconsin d. November 24, 1978 in New Milford, Connecticut) was an American scientist and mathematician.

Weaver graduated in 1919 at the University of Wisconsin with degrees in civil engineering and mathematics. He became an assistant professor of mathematics at Throop College (soon to be re-named the California Institute of Technology) before returning to teach mathematics at Wisconsin (1920–32). He was director of the division of natural sciences at the Rockefeller Foundation (1932–55), and was science consultant (1947–51), trustee (1954), and vice president (from 1958) at the Sloan-Kettering Institute for Cancer Research. Weaver's chief researches were in the problems of communication in science and in the mathematical theory of probability and statistics.

At the Rockefeller Foundation, he was responsible for approving grants for major projects in molecular engineering and genetics, in agriculture (particularly for developing new strains of wheat and rice), and in medical research. During World War II, he was seconded from the Foundation to head the Applied Mathematics Panel at the U.S. Office of Scientific Research and Development, directing the work of hundreds of mathematicians in operations research. He was therefore fully familiar with the development of electronic calculating machines and the successful application of mathematical and statistical techniques in cryptography.

He was co-author (together with Claude Shannon) of the landmark work on communication, The Mathematical Theory of Communication (1949, Urbana: University of Illinois Press). While Shannon focused more on the engineering aspects of the mathematical model, Weaver developed the philosophical implications of Shannon's much larger essay (which forms about 3/4th of the book).

Weaver had first mentioned the possibility of using digital computers to translate documents between natural human languages in March 1947 in a letter to the cyberneticist] Norbert Wiener. In the following two years, he had been urged by his colleagues at the Rockefeller Foundation to elaborate on his ideas. The result was a memorandum, entitled simply "Translation," which he wrote in July 1949 at Carlsbad, New Mexico (Reproduced in: Locke, W.N. and Booth, A.D. (eds.) Machine translation of languages: fourteen essays (Cambridge, Mass.: Technology Press of the Massachusetts Institute of Technology, 1955), pp. 15-23.)

Said to be probably the single most influential publication in the early days of machine translation, it formulated goals and methods before most people had any idea of what computers might be capable of, and was the direct stimulus for the beginnings of research first in the United States and then later, indirectly, throughout the world. The impact of Weaver’s memorandum is attributable not only to his widely recognized expertise in mathematics and computing, but also, and perhaps even more, to the influence he enjoyed with major policy-makers in U.S. government agencies.

Weaver’s memorandum was designed to suggest more fruitful methods than any simplistic word-for-word approach, which had grave limitations. He put forward four proposals. These were that the problem of multiple meanings might be tackled by the examination of immediate context; that it could be assumed that there are logical elements in language; that cryptographic methods were possibly applicable, and that there may also be linguistic universals.

At the end of the memorandum, Weaver asserted his belief in the fourth proposal with what is one of the best-known metaphors in the literature of machine translation: “Think, by analogy, of individuals living in a series of tall closed towers, all erected over a common foundation. When they try to communicate with one another, they shout back and forth, each from his own closed tower. It is difficult to make the sound penetrate even the nearest towers, and communication proceeds very poorly indeed. But, when an individual goes down his tower, he finds himself in a great open basement, common to all the towers. Here he establishes easy and useful communication with the persons who have also descended from their towers.”

Weaver early understood how greatly the tools and techniques of physics and chemistry could advance knowledge of biological processes, and used his position in the Rockefeller Foundation to identify, support, and encourage the young scientists who years later earned Nobel Prizes and other honours for their contributions to genetics or molecular biology.

He had a deep personal commitment to improving the public understanding of science. He was President of the American Association for the Advancement of Science in 1954 and Chairman of the Board in 1955, a member or chairman of numerous boards and committees, and the primary author of the Arden House Statement, a 1951 declaration of principle and guide to setting the Association's goals, plans, and procedures. In 1965 he was awarded the first Arches of Science Medal for outstanding contributions to the public understanding of the meaning of science to contemporary men and women, and UNESCO's Kalinga Prize for distinguished contributions to the popular understanding of science.

Weaver married Mary Hemenway, one of his fellow students at the University of Wisconsin, a few years after their graduation. They had a son, Warren Jr., and a daughter, Helen.