| 40th Wisconsin Infantry Regiment | |
|---|---|
 | |
| Active | June 14, 1864 – September 16, 1864 |
| Country | United States |
| Allegiance | Union |
| Branch | Infantry |
| Size | Regiment |
| Engagements | American Civil War |
| Commanders | |
| Colonel | W. Augustus Ray |
The 40th Wisconsin Infantry Regiment was a volunteer infantry regiment that served in the Union Army during the American Civil War. It was among scores of regiments that were raised in the summer of 1864 as Hundred Days Men, an effort to augment existing manpower for an all-out push to end the war within 100 days.