Sidney Robertson Cowell (born Sidney William Hawkins; 1903–1995) was an American ethnographer and the wife of the composer Henry Cowell. She was born in San Francisco, California.
She collected a large volume of American folk songs between 1936 and 1957, particularly for the WPA Northern California Folk Music Project (1938–1940), which she initiated.
She married in 1924, as her first husband, Kenneth Robertson. They later divorced.
In her later life, she lived in Shady, New York, United States.
While living in Shady, she sold her large library of books on Folklore and Folk Music to raise money for folklorist Vance Randolph, who needed funds to help him deal with medical problems.