Kent Cheng Jak-si (Chinese: 鄭則士, born 22 May 1951) is a Hong Kong film and television actor. He is a two time recipient of the best actor award at the Hong Kong Film Awards.
- Known For: Acting
- Birthday: 1951-05-22
- Place of Birth: Hong Kong
- Also Known As: Zeshi Zheng , Jui Si Cheng, Juk-Si Cheng, Ken Cheng, 정칙사, 郑则仕, Trịnh Tắc Sỹ, 鄭則仕