Charles Sprague "Carl" Ruggles (March 11, 1876 – October 24, 1971) was an American composer of the American Five group. He wrote finely crafted pieces using "dissonant counterpoint", a term coined by Charles Seeger to describe Ruggles' music. His method of atonal counterpoint was based on a non-serial technique of avoiding repeating a pitch class until a generally fixed number such as eight pitch classes intervened. He wrote painstakingly slowly so his output is quite small.

Famous for his prickly personality, Ruggles was nonetheless friends with Henry Cowell, Edgard Varèse, Charles Ives, Ruth Crawford Seeger, and Charles Seeger. His students include James Tenney and Merton Brown. Conductor Michael Tilson Thomas has championed Ruggles' music, recording the complete works with the Buffalo Philharmonic and occasionally performing Sun-Treader with the San Francisco Symphony. Especially later in life, Ruggles was also a prolific painter, selling hundreds of paintings during his lifetime.