Diana MacManus (born April 10, 1986) is a female backstroke swimmer from the United States.

As a member of the USA National team she competed at the 2001 Goodwill Games held in Brisbane, Australia where she won two silver medals.

At the 2002 Short Course World Championships in Moscow, Russia where she brought home two more bronze medals.

A native of San Diego, California, she was trained by coach Dave Salo of the Irvine Novaquatics from the age of 12.

She broke the USA's 11-12 age-group national record at age 12 in 50 yard backstroke, and at the age of 14, MacManus attempted to make the U.S. Olympic team in the 100m backstroke, finishing in fourth place in the U.S. Olympic trials.