Cassius Fairchild (December 16, 1829 – October 24, 1868) was a Wisconsin businessman, politician, and Union Army officer in the American Civil War.

[1] Cassius was the second of four sons born to Jairus Fairchild and Mrs. Sally Blair Fairchild—his older brother, Charles, died at age four in 1832.

At age fourteen, he traveled to the Wisconsin Territory with his uncle, Franklin J. Blair, arriving in the vicinity of Milwaukee.

Cassius and his brother, Lucius, were volunteers in a Wisconsin militia company known as the Governor's Guard in the late 1850s and gained experience that would become useful in securing leadership positions in the coming war.

He spent months recuperating, as surgeons attempted to remove the bullet and scraps of cloth that had been dragged into the wound.

The bullet and remaining pieces of material were finally removed by Dr. Brainerd in December 1862, but after months embedded in the bone, there was significant irritation around the wound that would, years later, result in Fairchild's death.

As Colonel, Fairchild led the regiment through Kennesaw Mountain, the Battle of Atlanta, and Sherman's March to the Sea.

On March 13, 1865, Fairchild was given a brevet to Brigadier General and commanded a Brigade composed of five regiments during the Battle of Bentonville.