George Day Wagner (September 22, 1829 – February 13, 1869) was an Indiana politician, farmer, and soldier, serving as a general in the Union Army during the American Civil War.

When he was four years old, Wagner's family moved to Warren County, Indiana, where he was educated in the common schools.

He was selected as the president of the Indiana State Agricultural Society, a post he held when the Civil War began in April 1861 with the bombardment of Fort Sumter in South Carolina.

In June of that year, Wagner enlisted in the state volunteer troops as colonel of the 15th Indiana Infantry and initially served in western Virginia.

[1] Federal reinforcements finally stabilized the position, but Wagner's controversial course of action drew significant criticism and questioning.

As a result of the debacle, Wagner asked to be relieved of duty, citing concerns for his wife's health.