William Newell Vaile (1876–1927) was an American lawyer, military veteran, and five-term U.S. Representative from Colorado. Born in Kokomo, Indiana, he moved with his family to Denver, Colorado, in 1881, where he grew up and attended public schools. He graduated from Yale University in 1898 and served in the Spanish-American War as a private in the Connecticut Volunteer Field Artillery.

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After the war, Vaile studied at the University of Colorado and Harvard Law School. He was admitted to the bar in 1901 and began his practice in Denver, representing the Denver & Rio Grande Railroad from 1901 to 1916. He also served as County Attorney for Jefferson County from 1911 to 1914. In 1916, he served on the Mexican border as a second lieutenant in the Colorado National Guard, following an unsuccessful bid for Congress that same year.

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In 1918, Vaile was elected as a Republican to the U.S. House of Representatives, where he served five consecutive terms from 1919 to 1927. During his tenure, he chaired the Committee on Expenditures in the Department of the Treasury and was a key figure in the passage of the Immigration Act of 1924. He was also known for co-sponsoring the Cummins-Vaile Bill, the first birth control legislation debated in Congress.

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Vaile died of a heart attack on 2 July 1927, while travelling near Rocky Mountain National Park. He is interred at Fairmount Cemetery in Denver, Colorado.