Henry Fountain Ashurst (September 13, 1874 – May 31, 1962) was an American Democratic politician and one of the first two senators from Arizona. Largely self-educated, he served as a district attorney and member of the Arizona Territorial legislature before fulfilling his childhood ambition of joining the United States Senate. During his time in the Senate, Ashurst was chairman of the Committee on Indian Affairs and the Judiciary Committee.

Called "the longest U.S. theatrical engagement on record" by Time, Ashurst's political career was noted for a self-contradictory voting record, for the use of a sesquipedalian vocabulary, and for a love of public speaking that earned him a reputation as one of the Senate's greatest orators. Among the sobriquets assigned to him were "the Dean of Inconsistency", "Five-Syllable Henry", and the "Silver-Tongued Sunbeam of the Painted Desert".

Ashurst was born on September 13, 1874, in an uncovered wagon near Winnemucca, Humboldt County, Nevada, to William and Sarah Ashurst, the second of ten children. His family moved to a ranch near Williams, Arizona, when he was two, and he attended school in Flagstaff. At the age of ten he showed his ambition to be a senator by writing "Henry Fountain Ashurst, U.S. Senator from Arizona" into a speller. After dropping out of school at the age of thirteen, he worked as a cowboy on his father's ranch.

At the age of nineteen, Ashurst was made the turnkey at the county jail in Flagstaff. While working at the jail, he developed an interest in the law by reading Blackstone's Commentaries. He later worked at a local lumber yard and studied law at night. In 1895, he worked as a lumberjack in the Los Angeles area and as a hod carrier in San Francisco. Following a brief return to Flagstaff, Ashurst enrolled at Stockton Business College (now Humphreys College), and graduated in 1896. Ashurst was admitted to the bar in 1897 and began a law practice in Williams. He completed his formal education with a year at the University of Michigan Law School beginning in 1903.

In 1904, Ashurst married Elizabeth McEvoy Reno, an Irish-born widow with one child from her first marriage. She had moved to Flagstaff with her children to establish and manage a Weather Bureau station. She served as his political advisor for the rest of her life. Mrs. Ashurst died on November 1, 1939.

Ashurst was elected to the Territorial House of Representatives in 1897. He was re-elected in 1899, and became the territory's youngest speaker. In 1902, he was elected to the Territorial Senate. He served as district attorney of Coconino County from 1905 to 1908, when he moved to Prescott, Arizona.

In 1911, Ashurst presided over Arizona's constitutional convention. During the convention, he positioned himself for a U.S. Senate seat by avoiding the political fighting over various clauses in the constitution which damaged his rivals.

With the admission of Arizona as a state in 1912, Ashurst was elected by the Arizona legislature as one of the state's two senators, taking office on April 2 alongside Marcus A. Smith. He was easily re-elected in 1916 (by popular vote), and again in 1922, 1928, and 1934, serving for almost 29 years. He sought re-election in 1940 but was defeated in the Democratic primary.