William Markley (Mark) Bellamy (born August 31, 1950)[1] is a retired American diplomat and US government senior official.

A career Foreign Service Officer, he served as United States ambassador to Kenya from 2003 to 2006 under President George W. Bush.

Bellamy's overseas assignments included Pollitical Counselor in South Africa (1991-1993), Political Minister-Counselor in France (1993-1997) and Deputy Chief of Mission in Australia (1997-2000).

In his role as United States Ambassador to Kenya (2003-2006), Bellamy directed security and counterterrorism programs in East Africa, oversaw the US government's largest overseas HIV-AIDS prevention and treatment program, and led international efforts to combat corruption and improve governance in Kenya.

In 2012, Bellamy was appointed Warburg Professor of Political Science and International Relations at Simmons University (Boston, MA).