Daniel Isaac J. Thornton (January 31, 1911 – January 19, 1976) was an American cattle breeder and Republican politician who served as the 33rd Governor of the State of Colorado from 1951 to 1955. Born in Texas, Thornton began his cattle operation in Arizona. He moved the business to Colorado in 1941. He entered politics in 1948, and was elected to the State Senate. In 1950, Thornton defeated incumbent Democratic Governor Walter Walford Johnson. Thornton was known for his Stetson hat, pipe, and cowboy boots. Among his accomplishments as governor was getting the United States Air Force to establish its academy in Colorado Springs. He was on the short list of candidates Dwight Eisenhower considered as his running mate in 1952 before he settled on Richard Nixon.
Thornton left politics after losing the U.S. Senate election in 1956. The City of Thornton was named in his honor.