William Ruger (died May 21, 1843) was an American lawyer and politician from New York.
About 1828, he opened a select school in Watertown, New York, and taught mathematics there. He published A New System of Arithmeticks (on-line copy; 1836; 264 pages). He also studied law, and was admitted to the bar in 1831. He practiced law in partnership with Charles Mason from 1835 to 1838.
Ruger was a member of the New York State Senate (5th D.) in 1842 and 1843.
Chief Judge William C. Ruger (1824–1892) was his nephew.