Steven Weinberg (/ˈwaɪnbɜːrɡ/; May 3, 1933 – July 23, 2021) was an American theoretical physicist and Nobel laureate in physics for his contributions with Abdus Salam and Sheldon Glashow to the unification of the weak force and electromagnetic interaction between elementary particles.

He held the Josey Regental Chair in Science at the University of Texas at Austin, where he was a member of the Physics and Astronomy Departments.

In 2004, he received the Benjamin Franklin Medal of the American Philosophical Society, with a citation that said he was "considered by many to be the preeminent theoretical physicist alive in the world today."

[13] He was in the same graduating class as Sheldon Glashow,[11] whose research, independent of Weinberg's, resulted in their (and Abdus Salam's) sharing the 1979 Nobel in physics.

After one year, Weinberg moved to Princeton University, where he earned his Ph.D. in physics in 1957, completing his dissertation, "The role of strong interactions in decay processes", under the supervision of Sam Treiman.

Weinberg's model, now known as the electroweak unification theory, had the same symmetry structure as that proposed by Glashow in 1961: both included the then-unknown weak interaction mechanism between leptons, known as neutral current and mediated by the Z boson.

the discovery of the inferred existence of the Z boson—but after the 1978 experimental discovery of the theory's predicted amount of parity violation due to Z bosons' mixing with electromagnetic interactions,[29] Weinberg was awarded the Nobel Prize in physics with Glashow and Salam, who had independently proposed a theory of electroweak unification based on spontaneous symmetry breaking.

[10][14] In 1982 Weinberg moved to the University of Texas at Austin as the Jack S. Josey-Welch Foundation Regents Chair in Science,[14] and started a theoretical physics group at the university that now has eight full professors and is one of the leading research groups in the field in the U.S.[10] Weinberg is frequently listed among the top scientists with the highest research effect indices, such as the h-index and the creativity index.

[30] The theoretical physicist Peter Woit called Weinberg "arguably the dominant figure in theoretical particle physics during its period of great success from the late sixties to the early eighties", calling his contribution to electroweak unification "to this day at the center of the Standard Model, our best understanding of fundamental physics".

[33] Brian Greene said that Weinberg had an “astounding ability to see into the deep workings of nature” that “profoundly shaped our understanding of the universe".

[33] Upon the awarding of the Breakthrough Prize in 2020, one of the founders of the prizes, Yuri Milner, called Weinberg a “key architect” of “one of the most successful physical theories ever”, while string theorist Juan Maldacena, the chair of the selection committee, said, “Steven Weinberg has developed many of the key theoretical tools that we use for the description of nature at a fundamental level".

[39] In 2016, Weinberg became a default leader for faculty and students opposed to a new law allowing the carrying of concealed guns in UT classrooms.