Madelyn or Madalyn is a feminine first name. Notable people with these names include:

• Madelyn Clare (1894–1975), American actress
• Madelyn Cline (born 1997), American actress
• Maddy Curley (born 1981), American actress
• Madelyn Desiano (born 2000), American soccer player
• Madelyn Deutch (born 1991), American actress
• Madelyn Dunham (1922–2008), maternal grandmother of Barack Obama
• Madelyn Pugh (1921–2011), American television writer who worked on the I Love Lucy television series
• Madelyn Renee (born 1955), American soprano formerly known as Madelyn Renée Monti
• Madelyn Rosenberg (born 1966), American author
• Madelyn Vega, Puerto Rican journalist and attorney

• Madalyn Aslan (born 1963), American-British writer, astrologer, and palmist
• Madalyn Godby (born 1992), American track cyclist
• Madalyn Murray O'Hair (1919–1995), American writer and activist
• Madalyn Schiffel (born 1994), American soccer goalkeeper

• Madelyn "Maddie" Hayes, in the television series Moonlighting
• Madelyn Stillwell, in the television series The Boys and The Boys Presents: Diabolical
• Madelyn Spaulding, a villain from Static Shock

• Madlyn (given name)