Michael J. Ryan may refer to:Michael J. Ryan (athlete) (1889–1971), winner of the 1912 Boston Marathon Michael J. Ryan (biologist), American biologist Michael J. Ryan (doctor), Irish epidemiologist, surgeon, and chief executive director of the WHO Health Emergencies Programme Michael J. Ryan, Irish barrister, professor and politician Michael J. Ryan (1862–1943), president of the United Irish League of America Michael James Ryan or Mike Ryan (1941–2020), American baseball player Michael Joseph Ryan (footballer) or Mike Ryan (1930–2006), English footballer Michael Joseph Ryan or Rocky Ryan (1937–2004), British media hoaxer