Ethel Watts Mumford was an American author from New York City. The surname Mumford came from her first husband, George D. Mumford, a lawyer.

After her first husband grew intolerant of her prolific writing and art career, she fled to San Francisco in 1899 with their only child, a son. She sued for divorce on grounds of desertion. After the divorce was granted in 1901, she returned to New York, vowing never to remarry unless her husband accepted her career. On June 4, 1906 she married Peter Geddes Grant of Grantown, Morayshire, Scotland.

The daughter of a wealthy businessman, she was given a fine education, topped by her study of painting at the Julian Academy of Paris. She traveled extensively in Europe, the Far East, and North America, experience that is well-reflected in her work.

Most of her early published works were written in San Francisco including her first novel, Dupes. She was a heavy producer of plays, vaudeville sketches, novels, short stories, joke collections, songs, poems, and articles. She also painted and illustrated books.

In her teen years, after studying dramatic technique by reading 2,000 manuscripts, she turned to playwriting. Her farces were produced on New York and London stages. After her 1906 marriage she wrote for a time under the name "Ethel Watts Mumford Grant," adding her second husband's name, but eventually reverted to "Ethel Watts Mumford" as a byline.