Cheng Kaijia (Traditional Chinese: 程開甲, Simplified Chinese: 程开甲, Pinyin: Chéng Kāijiǎ) (August 3, 1918 –), also known as Cheng Kai-jia or Cheng Kai Jia, is a Chinese nuclear physicist and engineer. He is a pioneer and key figure in Chinese nuclear weapon development.
Cheng was born in Wujiang County, Jiangsu Province in 1918. He graduated from the Department of Physics, of Zhejiang University in 1941. In 1946, he went to Britain and studied at the University of Edinburgh, and obtained a PhD in 1948 (advisor: Max Born). He then became a researcher in the UK.
Cheng returned to China in 1950. He was an associate professor at Zhejiang University, he then went to Nanjing, where he became an associate professor in Nanjing University, and was later promoted to full professorship.
Cheng was a pioneer of Chinese nuclear technology and played an important role in the development of the first Chinese atomic bomb. He first calculated out the inner temperature and pressure for an atomic bomb blast in China. His calculation was an extremely heavy task and nearly manual, because during that time China did not have any computer or even calculator. He also solved the mechanism of the inner explosion, which could support the design of the bomb. He was the chief director for many nuclear weapon test fields/bases and their explosion processes.
Cheng was elected to the Chinese Academy of Sciences. He was also a Standing Member of the Science and Technology Committee, Chinese National Nuclear Industry Corporation. He was former Vice-President of the Nuclear Weapons Research Institute, and the Deputy Chief Director of the Nuclear Weapons Research Institute, People's Republic of China. 
- 596 - China's first nuclear weapons test.
- 中国的"核司令"程开甲 Cheng Kai-jia, China's Nuclear Commander
- Chen Kaijia's biography in Baidu.com “我国第一颗原子弹研制的开拓者之一，我国核武器试验事业的创始人之一。在国内第一个计算出原子弹爆炸的弹心温度和压力，其内爆机理研究解决了原子弹的关键问题，为原子弹爆炸威力、弹体结构设计提供了重要依据。……”
- ChinaVitae the biography highlight of Cheng Kaijia
- ChinaVitae - the biography highlight of Cheng Kaijia
- Holeung Ho Lee Foundation (HHLF) AWARDEE OF TECHNOLOGICAL SCIENCES PRIZE - CHENG KAIJIA (Abstract)
- 两弹一星功勋：核武器专家程开甲院士 Nuclear weapon pioneer - Academician Cheng Kaijia (Chinese)