Curtis Tracy McMullen (born May 21, 1958) is an American mathematician who is the Cabot Professor of Mathematics at Harvard University.

He was awarded the Fields Medal in 1998 for his work in complex dynamics, hyperbolic geometry and Teichmüller theory.

McMullen graduated as valedictorian in 1980 from Williams College and obtained his PhD in 1985 from Harvard University, supervised by Dennis Sullivan.

His doctoral student Maryam Mirzakhani was the first woman to win the Fields Medal.

McMullen received the Salem Prize in 1991 and won the Fields Medal in 1998[1][2] at the International Congress of Mathematicians (ICM) in Berlin.