Mary Ryan may refer to:

• Mary Ryan (actress) (1885-1948), American stage and screen actress
• Mary Nash (1884–1976), American vaudevillian, later stage/screen actress, whose birth name was Mary Ryan

• Mary Ryan (a.k.a. Blue Mary), in the Fatal Fury and The King of Fighters computer game series, voiced by Harumi Ikoma (FF3–KOF: MIR"A") and Sarah Emi Bridcutt (KOF XIV onwards)
• Mary Ryan (character), in the US soap opera Ryan's Hope, played by Kate Mulgrew (1975–1978, 1983, 1986, 1989), Mary Carney (1978), Kathleen Tolan (1978–1979), and Nicolette Goulet (1979)
• Mary Ryan, in the 1999 Canadian film The Divine Ryans, played by Genevieve Tessier

• Mary Ryan, Dublin camogie player, who played in 1964 All-Ireland Senior Camogie Championship
• Mary Ryan, Galway camogie player, who played in Gael Linn Cup 1981
• Mary Ryan, Tipperary camogie player, who played in 2006 All-Ireland Senior Camogie Championship

• Mary Alma Ryan (1863–1929), American Roman Catholic nun
• Mary Ryan (academic) (1873–1961), first woman professor in Ireland or Great Britain
• Mary Ryan (Irish politician) (1898–1981), Irish Fianna Fáil TD for Tipperary 1944–1961
• Mary A. Ryan (1940–2006), U.S. diplomat
• Mary P. Ryan, American historian
• Mary Ryan (writer), American TV writer/director
• Mary Perkins Ryan (1912–1993), American Catholic author, editor, and educator
• Mary Ryan (materials scientist), professor of materials science
• Mary Kate Ryan (1878–1934), Irish academic and political activist
• Mary Eucharia Ryan (1860–1929), Irish Loreto sister and pioneer of women's higher education
• Mary Ryan, who spotted Momo the Monster

• Mary Ryan, Detective, a 1949 American crime drama
• Marie Ryan (disambiguation)