Clarence D. Clark (April 16, 1851 - November 18, 1930) was a teacher, lawyer, and politician from New York who participated in the constitutional convention for Wyoming's statehood and was one of that state's first congressmen.
He was born in Sandy Creek, New York and attended the University of Iowa at Iowa City. He studied law and was admitted to the bar in 1874. He subsequently both wasa teacher and practiced law in Manchester, Iowa. In 1881, he moved to Evanston, Wyoming and continued to practice law before becoming the county attorney of Uinta County, a job he held between 1882 and 1884.
In 1889, he began his political career as a delegate to the Wyoming constitutional convention. he subsequently ran for the United States House of Representatives and became one of the new state's first representatives. He remained in office two terms, from 1890 to 1893, before losing the 1892 election. He was elected as a United States Senator in a special election to fill a vacancy in 1895 and was re-elected to that seat three times and served until 1917.
After losing the election in 1916, he resumed the practice of law in Washington, D.C., but was appointed as a member of the International Joint Commission in 1919. He served as its chairman from 1923 until his retirement in 1929. After retirement, he moved back to Evanston, Wyoming until his death in 1930.