Lyman Rufus Casey Jr. (May 6, 1837 – January 26, 1914) was a United States senator from North Dakota.

Casey 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 4, 1893.

[1] One of her siblings was Jane Platt, wife of the drinking straw inventor Marvin C.