Isaac Ferdinand Quinby (January 29, 1821 – September 18, 1891) was a U.S. soldier and Union general during the American Civil War.

In August of that year he resigned from the army but on March 17, 1862, was appointed brigadier general of volunteers[1] and sent to the Western Theater to command the Sub-district of Columbus.

[3] In March 1863 Admiral David D. Porter and General Leonard F. Ross led the Yazoo Pass Expedition against Confederate-held Fort Pemberton.

Having recovered, Quinby returned to duty on the morning of May 16 but it was deemed necessary for General Crocker to retain command of the division as they were deploying for Battle at Champion Hill.

During the siege, on June 3, Quinby’s health began to fail him again, and went on another sick leave, only this time he would not return to field command.