| Unit Name: | 21st Regiment Kansas Militia Infantry |
| Dates: | October 9, 1864 - October 29, 1864 |
| Country: | United States |
| Allegiance: | Union |
| Branch: | Infantry |
| Battles: | Battle of Byram's Ford Battle of Westport |
The 21st Kansas Militia Infantry was an infantry regiment that served in the Union Army during the American Civil War.
The 21st Kansas Militia Infantry was called into service on October 9, 1864. It was disbanded on October 29, 1864.
The unit was called into service to defend Kansas against Maj. Gen. Sterling Price's raid. The regiment saw action at Byram's Ford, Big Blue, October 22. Westport October 23.