Daniel Harry Friedan (born October 3, 1948) is an American theoretical physicist and a professor at Rutgers University. He is one of three children of the feminist author and activist Betty Friedan.

Friedan earned his Ph.D. from the University of California, Berkeley in 1980 and was named a MacArthur Fellow in 1987.

In 1979, he showed that the equations of motions of string theory, which are generalizations of the Einstein equations of general relativity, emerge from the renormalization group equations for the two-dimensional field theory.

Friedan has worked in string theory and condensed matter theory, specializing in (1 + 1)-dimensional systems. His current research focuses on applications to quantum computers.

Friedan received the 2010 Lars Onsager Prize from the American Physical Society "for seminal work on the classification and characterization of two-dimensional unitary conformal field theories of critical states." He currently teaches at Rutgers University.

Daniel is married to an Icelandic physics teacher, Ragnheiður Guðmundsdóttir. They have two daughters and one son together.