Tsung-Dao Lee (T.D. Lee, Chinese: 李政道; pinyin: Lǐ Zhèngdào) (born November 24, 1926) is a Chinese born American physicist, well known for his work on parity violation, the Lee Model, particle physics, relativistic heavy ion (RHIC) physics, nontopological solitons and soliton stars.

In 1957, Lee, at the age of 30 (with C.N. Yang) won the Nobel Prize in Physics for their work on the violation of parity law in weak interaction, which Chien - Shiung Wu experimentally verified. Lee is the youngest Nobel laureate after World War II, and the third youngest in history after W.L. Bragg (who won the prize at 25 with his father W.H. Bragg in 1915) and Werner Heisenberg (who won in 1932 also at 30). Lee and Yang were the first Chinese laureates. Since naturalized as American citizen in 1962, Lee thus is also the youngest American who has ever won a Nobel Prize.

Tsung Dao (T.D.) Lee's ancestral hometown is Suzhou, Jiangsu Province. T.D. was born in Shanghai. Lee's father Chun-kang Lee (simplified Chinese: 李骏康; traditional Chinese: 李駿康; pinyin: Lǐ Jùn-kāng), one of the first graduates of the University of Nanking, was a chemical industrialist and merchant who was involved in China's early development of modern synthesized fertilizer. Lee's grandfather Chong-tan Lee (Chinese: 李仲覃; pinyin: Lǐ Zhòng-tán) was the first Chinese Catholic rector in Suzhou whose residence was the famous St.John's Church in Suzhou (蘇州聖約翰堂). Lee has four brothers and one sister. Educator Robert C.T. Lee is one of T.D.'s brothers. Lee's mother Chang and brother Robert C.T. moved to Taiwan, but were jailed in 1950s during the White Terror period of Taiwan. Chang died in Taipei and her ashes were brought back and buried in Suzhou.

Lee received his secondary education in Shanghai and Jiangxi. Due to the Second Sino - Japanese war, Lee's high school education was interrupted, thus he did not obtain his secondary diploma. Nevertheless, in 1943, Lee directly applied and was admitted by the National Chekiang University (now Zhejiang University). Initially, Lee registered as a student in the Department of Chemical Engineering. Very quickly, Lee's talent was discovered and his interest in physics grew rapidly. Several physics professors, including Shu Xingbei and Kan-Chang Wang, largely guided Lee, and he soon transferred into the Department of Physics of Zhejiang University, where he studied in 1943 – 1944. However, again disrupted by a further Japanese invasion, Lee continued at the National Southwestern Associated University (國立西南聯合大學) in Kunming the next year in 1945, where he studied with Professor Ta-You Wu.

Professor Wu nominated Lee for a Chinese government fellowship for graduate study in USA. In 1946, Lee went to the University of Chicago and was selected by Professor Enrico Fermi to become his PhD student. Lee completed his PhD thesis under Fermi in 1950. Lee served as research associate and lecturer in physics at the University of California at Berkeley from 1950 to 1951.

In 1953, Lee joined Columbia University, where he remains today. His first work at Columbia was on a solvable model of quantum field theory better known as the Lee Model. Soon, his focus turned to particle physics and the developing puzzle of K meson decays. Lee realized in early 1956 that the key to the puzzle was parity non-conservation. At Lee's suggestion, the first experimental test was on hyperion decay by the Steinberger group. At that time, the experimental result gave only an indication of a 2 standard deviation effect of possible parity violation. Encouraged by this feasibility study, Lee made a systematic study of possible P, T, C and CP violations in weak interactions with collaborators, including C.N. Yang. After the definitive experimental confirmation by C.S . Wu and her collaborators of parity non-conservation, Lee and Yang were awarded the 1957 Nobel Prize for Physics.

In the early 1960s, Lee and collaborators initiated the important field of high energy neutrino physics. In 1964, Lee, with M. Nauenberg, analyzed the divergences connected with particles of zero rest mass, and described a general method known as the KLN theorem for dealing with these divergences, which still plays an important role in contemporary work in QCD, with its massless, self - interacting gluons. In 1974 – 75, Lee published several papers on "A New Form of Matter in High Density", which led to the modern field of RHIC physics, now dominating the entire high energy nuclear physics field.

Besides particle physics, Lee has been active in statistical mechanics, astrophysics, hydrodynamics, many body system, solid state, lattice QCD. In 1983, Lee wrote a paper entitled, "Can Time Be a Discrete Dynamical Variable?"; which led to a series of publications by Lee and collaborators on the formulation of fundamental physics in terms of difference equations, but with exact invariance under continuous groups of translational and rotational transformations. Beginning in 1975, Lee and collaborators established the field of non-topological solitons, which led to his work on soliton stars and black holes throughout the 1980s and 1990s.

From 1997 to 2003 Lee was director of the RIKEN - BNL Research Center (now director emeritus), which together with other researchers from Columbia, completed a 1 teraflops supercomputer QCDSP for lattice QCD in 1998 and a 10 teraflops QCDOC machine in 2001. Most recently, Lee and R. Friedberg have developed a new method to solve the Schrödinger Equation, leading to convergent iterative solutions for the long standing quantum degenerate double - wall potential and other instanton problems. They have also done work on the neutrino mapping matrix.

Soon after the re-establishment of China - American relations with the PRC, Lee and his wife, Hui-Chun Jeannette Chin (Chinese: 秦惠䇹; pinyin: Qín Huìjūn), were able to go to China, where Lee gave a series of lectures and seminars, and organized the CUSPEA (China - U.S. Physics Examination and Application).

In 1998, Lee established the Chun-Tsung Endowment (秦惠䇹—李政道中国大学生见习基金) in memory of his wife, Hui-Chun Chin, who died 3 years earlier. The Chun-Tsung scholarships, supervised by the United Board for Christian Higher Education in Asia (New York), are awarded to undergraduates, usually in their 2nd or 3rd year, at five universities, which are Fudan University, Lanzhou university, Suzhou University, Peking University and Taiwan National Tsing Hua University. Students selected for such scholarships are named "Chun-Tsung Scholars" (䇹政学者).

Chin and Lee were married in 1950 and have two sons: James and Stephen. Lee reads whodunit novels when not working on physics. His English given name differs dramatically from the Chinese Romanization systems in use at the time of his childhood, Wade - Giles and Gwoyeu Romatzyh. Tsung-Dao Lee's publications are all under the name of T.D. Lee.