Steven Chu (born February 28, 1948), is a physicist and currently the 12th United States Secretary of Energy. As a scientist, Chu is known for his research in cooling and trapping of atoms with laser light, which won him the Nobel Prize in Physics in 1997. At the time of his appointment as Energy Secretary, he was a professor of physics and molecular and cellular biology at the University of California, Berkeley and the director of the Lawrence Berkeley National Laboratory, where his research was concerned primarily with the study of biological systems at the single molecule level. He is a vocal advocate for more research into alternative energy and nuclear power, arguing that a shift away from fossil fuels is essential to combat global warming.

Chu, a Chinese American, was born in St. Louis, Missouri, with ancestry from Taicang, in Jiangsu province, and graduated from Garden City High School. He received his bachelor’s degree in 1970 from the University of Rochester, and his doctorate degree from University of California, Berkeley in 1976, during which he was supported by a National Science Foundation Graduate Research Fellowship.

Chu comes from a family of scholars. His father earned an advanced chemical engineering degree at the Massachusetts Institute of Technology and taught at Washington University in St. Louis and Brooklyn Polytechnic Institute, while his mother studied economics. His maternal grandfather earned advanced civil engineering degrees at Cornell University and his mother's uncle, Li Shu-hua, a notable physical scientist, studied physics at the Sorbonne before they returned to China. His older brother Gilbert Chu is a professor and researcher of biochemistry and medicine at Stanford University. His younger brother, Morgan Chu, is a partner and the former Co-Managing Partner at the law firm Irell & Manella LLP. According to Chu, his two brothers and four cousins earned three M.D.s, four Ph.D.s, and a J.D. among them. In 1997, he married Jean Fetter, a British American and an Oxford-trained physicist. He has two sons, Geoffrey and Michael, from a previous marriage to Lisa Chu-Thielbar.