The Battle of Fort Ridgely was an early battle in the Dakota War of 1862. As the closest U.S. military post to the Lower Sioux Agency, the lightly fortified Fort Ridgely quickly became both a destination for refugees and a target of Dakota warbands after the attack at the Lower Sioux Agency. It came under attack by the Dakota on August 20, 1862, two days after a company of soldiers responding from the fort to the attack on the Lower Sioux Agency had been ambushed and defeated at the Battle of Redwood Ferry. The Dakota besieged and partially destroyed the fort, but were unable to storm it before the August 27 arrival of Colonel Henry Sibley with 1,400 men from Fort Snelling prompted them to retreat.

The Dakota War of 1862, also known as the Sioux Uprising, the Dakota Uprising, the Sioux Outbreak of 1862, the Dakota Conflict, or Little Crow's War, was an armed conflict between the United States and several eastern bands of Dakota collectively known as the Santee Sioux. It began on August 18, 1862, when the Dakota, who were facing starvation and displacement, attacked white settlements at the Lower Sioux Agency along the Minnesota River valley in southwest Minnesota. The war lasted for five weeks and resulted in the deaths of hundreds of settlers and the displacement of thousands more. In the aftermath, the Dakota people were exiled from their homelands, forcibly sent to reservations in the Dakotas and Nebraska, and the State of Minnesota confiscated and sold all their remaining land in the state. The war also ended with the largest mass execution in United States history with the hanging of 38 Dakota men.