William A. Massey (October 7, 1856 - March 5, 1914) was a United States Senator from Nevada. Born in Oakfield, Ohio, he moved with his parents to Edgar County, Illinois in 1865. He attended the common schools, Union Christian College in Merom, Indiana, and the Indiana Asbury University (now De Pauw University) in Greencastle, Indiana. He studied law, and was admitted to the bar in 1877, commencing practice in Sullivan, Indiana. He moved to San Diego, California in 1886, and to Nevada in 1887, where he prospected and mined, and later took up the practice of law in Elko, Nevada.
Massey was a member of the Nevada Assembly from 1892 to 1894, and was district attorney from 1894 to 1896. He was a justice of the State supreme court from 1896 to 1902, when he resigied. He moved to Reno, Nevada and resumed the practice of law, and was appointed as a Republican to the United States Senate to fill the vacancy caused by the death of George S. Nixon; he served in the Senate from July 1, 1912 to January 29, 1913, when a successor was elected. He was an unsuccessful candidate for election to the remainder of Nixton's term ending March 3, 1917. While in the Senate, he was chairman of the Committee on Mines and Mining.
After his time in the Senate, he resumed the practice of law in Reno, and died on a train near Litchfield, Nevada in March of 1914. His interment was in Mountain View Cemetery in Reno.