Lyman R. Casey (May 6, 1837 - January 26, 1914) was a United States Senator from North Dakota. Born in York, New York, he moved with his parents to Ypsilanti, Michigan in 1853. He received a classical education and engaged in the hardware business for many years; in 1882, he moved to Carrington, Foster County, Territory of Dakota, and became a rancher. He was chairman of the North Dakota Committee on Irrigation and was commissioner of Foster County in 1887.
Upon the admission of North Dakota as a State into the Union, Casey was elected as a Republican to the U.S. Senate and served from November 25, 1889, to March 3, 1893. He was an unsuccessful candidate for renomination in 1892. While in the Senate, he was chairman of the Committee on Railroads (Fifty-second Congress). He moved to New York City, and then returned to Washington, D.C., and died there in 1914. Interment was in Greenmount Cemetery, Baltimore, Maryland.