Chih-Kung Jen (Chinese: 任之恭; pinyin: Rén Zhīgōng; August 15 or October 2, 1906 – November 19, 1995) was a Chinese physicist who emigrated to the U.S. and participated in some of the 20th century's major scientific, political and social developments in both the United States and China.

Born in a mud house in a remote and largely illiterate village in China, he was awarded a scholarship funded as a result of the Boxer Rebellion of the late 19th century to attend Beijing's prestigious Tsinghua University. As part of that scholarship, he came to the U.S. in 1926 to study electrical engineering and physics at MIT. He completed his graduate studies first at the University of Pennsylvania, and then in physics at Harvard University. Jen was among the first to provide experimental proof of the existence of the ionosphere. In addition, he obtained the first theoretically calculated value for the electron affinity spectrum of the hydrogen atom, a problem of fundamental significance in quantum mechanics and astrophysics.

In 1937, Jen returned to China, and subsequently joined in the "Academic Long March" to set up a wartime refugee university (the National Southwestern Associated University) in Kunming. His wartime teaching and research contributed to the training of what would become the nucleus of the present-day Chinese scientific intelligentsia.

After the war, Jen returned to the Physics Department at Harvard, and eventually settled at the Applied Physics Laboratory at Johns Hopkins University to carry on pioneering research in trapping free radicals and other topics in microwave spectroscopy.

In 1972, following Richard Nixon's visit to China, Jen led a ground-breaking delegation of Chinese American scientists to that country. The delegation conferred with Premier Zhou Enlai, and initiated what was to become a steady stream of scientific exchanges between the U.S. and China. Jen subsequently made numerous visits to China. He continued to work on strengthening U.S.-China scientific relations, and in addition was a leader in improving scientific education in Chinese universities.