Yang Chen-Ning (simplified Chinese: 杨振宁; traditional Chinese: 楊振寧; pinyin: Yáng Zhènníng; October 1, 1922 – October 18, 2025) also known as C.N. Yang and Franklin Yang, was a Chinese-American theoretical physicist who made significant contributions to statistical mechanics, integrable systems, gauge theory, particle physics and condensed matter physics.
Yang is known for his collaboration with Robert Mills in 1954 in developing non-abelian gauge theory, widely known as the Yang–Mills theory, which describes the nuclear forces in the Standard Model of particle physics.
Yang and Tsung-Dao Lee received the 1957 Nobel Prize in Physics for their work on parity non-conservation of the weak interaction, which was confirmed by the Wu experiment in 1956. The two proposed that the conservation of parity, a physical law observed to hold in all other physical processes, is violated in weak nuclear reactions – those nuclear processes that result in the emission of beta particles.
Yang was born in Hefei, Anhui, China, on October 1, 1922. His mother was Luo Meng-hua and his father, Ko-Chuen Yang (楊克純; 1896–1973), was a mathematician.
Yang attended elementary school and high school in Beiping (now Beijing), and in the autumn of 1937 his family moved to Hefei after the Japanese invaded China. In 1938 they moved to Kunming, Yunnan, where National Southwestern Associated University was located. In the same year, as a second-year student, Yang passed the entrance examination and studied at National Southwestern Associated University. He received a Bachelor of Science in 1942, with his thesis on the application of group theory to molecular spectra, under the supervision of Ta-You Wu.
Yang continued to study graduate courses there for two years under the supervision of Wang Zhuxi (J.S. Wang), working on statistical mechanics. In 1944, he received a Master of Science from National Tsing Hua University, which had moved to Kunming during the Sino-Japanese War (1937–1945). Yang was then awarded a scholarship from the Boxer Indemnity Scholarship Program, set up by the United States government using part of the money China had been forced to pay following the Boxer Rebellion. His departure for the United States was delayed for one year, during which time he taught in a middle school as a teacher and studied field theory.
Yang entered the University of Chicago in January 1946 and studied with Edward Teller. He received a Doctor of Philosophy in 1948.
Yang remained at the University of Chicago for a year as an assistant to Enrico Fermi. In 1949 he was invited to do his research at the Institute for Advanced Study in Princeton, New Jersey, where he began a period of fruitful collaboration with Tsung-Dao Lee. Lee and Yang published 32 papers together. He was made a permanent member of the Institute in 1952, and full professor in 1955. In 1963, Princeton University Press published his textbook, Elementary Particles. In 1965 he moved to Stony Brook University, where he was named the Albert Einstein Professor of Physics and the first director of the newly founded Institute for Theoretical Physics. Today this institute is known as the C. N. Yang Institute for Theoretical Physics. Yang retired from Stony Brook University in 1999.
Yang visited the Chinese mainland in 1971 for the first time after the thaw in China–US relations, and subsequently worked to help the Chinese physics community rebuild the research atmosphere, which later eroded due to political movements during the Cultural Revolution. After retiring from Stony Brook, he returned to Beijing as an honorary director of Tsinghua University, where he was the first Huang Jibei-Lu Kaiqun Professor at the Center for Advanced Study (CASTU). He was also one of the two Shaw Prize Founding Members and was a Distinguished Professor-at-Large at the Chinese University of Hong Kong.
Yang helped to establish the Theoretical Physics Division at the Chern Institute of Mathematics in 1986 at the request of Shiing-Shen Chern who was serving as the inaugural director of the Institute at the time.
Yang married Tu Chih-li (traditional Chinese: 杜致禮; simplified Chinese: 杜致礼; pinyin: Dù Zhìlǐ), a teacher, in 1950; they had two sons and a daughter together. His father-in-law was the Kuomintang general Du Yuming. Tu died in October 2003. In January 2005, Yang married Weng Fan (Chinese: 翁帆; pinyin: Wēng Fān), a university student. They met in 1995 at a physics seminar; the couple reestablished contact in February 2004 when Yang moved to China to become affiliated with Tsinghua University. Yang called Weng, who was 54 years his junior, his "final blessing from God".
Yang obtained U.S. citizenship during his research within the country. According to the state-run Xinhua News Agency, Yang said the decision was painful as his father never forgave him for that. According to Xinhua and other mainstream Chinese media, he formally renounced his American citizenship on April 1, 2015. He acknowledged that while the U.S. was a beautiful country that gave him good opportunities to study science, China since his youth had offered the best secondary and undergraduate institutions, though the US had the top graduate studies. However, circumstances changed in favor of China's growth by the turn of the century.
His son Guangnuo was a computer scientist. His second son Guangyu is an astronomer, and his daughter Youli is a doctor.
Yang turned 100 on October 1, 2022, and died in Beijing on October 18, 2025, at the age of 103. The day after the announcement of his death, people gathered and waited in line at Tsinghua University to pay tributes to Yang.
Yang is known for having opposed the construction of the Circular Electron Positron Collider (CEPC), a 100 km circumference particle collider in China that would study the Higgs boson. He catalogued the project as "guess" work and without guaranteed results. Yang said that "even if they see something with the machine, it's not going to benefit the life of Chinese people any sooner."
Yang worked on statistical mechanics, condensed matter theory, particle physics and gauge theory/quantum field theory.
Various Nobel Prizes in Physics are based on Yang's work. At least 10 Nobel laureates in Physics cited Yang's work during their Nobel speech, this includes: Steven Weinberg (1979), Sheldon Glashow (1979), Martinus J. G. Veltman (1999), Gerard 't Hooft (1999), David Gross (1999), Yoichiro Nambu (2008), Makoto Kobayashi (2008), Toshihide Maskawa (2008), François Englert (2013) and Peter Higgs (2013).
His first two papers (1944, 1945) were the result of his master thesis on statistical physics, supervised by J. S. Wang.