Silas Casey (July 12, 1807 – January 22, 1882) was a career United States Army officer who rose to the rank of major general during the American Civil War (1861-1865).

After the Mexican-American War, he performed frontier duties and escorted topographical parties, including a trip to California around Cape Horn in 1849.

Gen. George McClellan blamed them for the disaster, in spite of the fact that it was the smallest, least experienced, and least well-equipped division in the army and clearly should not have been placed in such a vulnerable location as the Seven Pines crossroads.

For the remainder of the Peninsula Campaign, Casey and his former division were relegated to a post around army headquarters at Harrison's Landing and kept away from the front lines.

After the Seven Days battles, when McClellan conducted a review of the army, the soldiers in Casey's division turned their backs and refused to cheer him.

In December 1862 he was appointed to the board that ultimately convicted Maj. Gen. Fitz John Porter of disobedience and cowardice for his actions at the Second Battle of Bull Run.