Fort Ripley was a United States Army outpost on the upper Mississippi River, in mid-central Minnesota from 1848 to 1877. It was situated a few miles from the Indian agencies for the Ho-Chunk and Ojibwe in Iowa Territory and then the Minnesota Territory. Its presence spurred immigration into the area and the pioneer settlement of Crow Wing developed approximately 6.75 miles (10.86 km) north of the fort. The post was initially named Fort Marcy. It then was renamed Fort Gaines and in 1850 was renamed again for distinguished Brigadier General Eleazer Wheelock Ripley of the War of 1812. It was the second major military reservation established in what would become Minnesota.

In 1971 Fort Ripley was listed on the National Register of Historic Places for its state-level significance in the historical archaeology and military history categories. It was nominated for its status as Minnesota's second major military post and for its role in maintaining peace and enabling pioneer settlement in Central Minnesota.

Camp Ripley, a training facility of the Minnesota National Guard, was established in 1929. It includes the historic site of Fort Ripley and was named in its honor. The nearby city of Fort Ripley, Minnesota, was also named for the old outpost.

Fort Ripley typified remote mid-19th century army posts. The buildings were of timber construction, facing a quadrangle. The fort had a partial stockade with the side facing the river completely open except for two of the three block houses. It was on a navigable river and an important trade route. The location was geographically remote to Colonial-American population centers, with Native Americans living in the vicinity.

Fort Ripley was built in conjunction with the Ho-Chunk had been moved from northeastern Iowa. Their new reservation near Long Prairie, Minnesota, necessitated a military post nearby to oversee the reservation and administer annuity payments. The government also hoped that the Ho-Chunk, and the fort, would serve as a buffer between the Santee Dakota and the Chippewa, who were warring. Construction began in November 1848. In April 1849, Company A of the 6th Infantry Regiment arrived from Fort Snelling to take up quarters under the command of Captain John Blair Smith Todd. With them were men of Company D 1st Dragoons commanded by 2nd Lt. John W.T. Gardiner.

Commanders and officers:

With occasional exceptions, daily life at Fort Ripley was uneventful. The geographic isolation, summer mosquitoes, and long, cold winters made post life challenging. The Metis oxcart trains traversing the eastern route of the Red River Trails between Selkirk – Fort Garry and the American Fur Trading outpost at Mendota/Fort Snelling(later Saint Paul) passed Fort Ripley. Twice each year, the soldiers trekked to the Long Prairie Agency to supervise government annuity payments of money and goods to the Ho-Chunk/Winnebago and then did the same for the Ojibwe/Chippewa at the Crow Wing Agency.

On July 18, 1850, Congress approved funds to build five military roads in the Minnesota Road Act. Two originated on Point Douglas, Minnesota at the confluence of the St. Croix and Mississippi Rivers. The first was named the Fort Ripley Military Wagon Road. It went north through Cottage Grove, Newport, St. Paul, St. Anthony Falls to Crow Wing seven miles past Fort Ripley. The distance from St. Paul to Fort Ripley via the wagon road was 150 miles.