Wanniarachchi is a surname. Notable people with the surname include:
Dharmadasa Wanniarachchi (1921-2007), Sri Lankan politician Manju Wanniarachchi (born 1979), Sri Lankan amateur boxer Neranjana Wanniarachchi (born 1998), Sri Lankan cricketer Pavithra Wanniarachchi, Sri Lankan politician Thisuri Wanniarachchi, Sri Lankan author