Gardiner is a census-designated place (CDP) in Park County, Montana, United States, along the 45th parallel. The population was 875 at the 2010 census.
Gardiner was officially founded in 1880, but the area has served as a main entrance to Yellowstone National Park since its creation in 1872. Parks' Fly Shop, one of the oldest fly shops and guiding operations in the Yellowstone area, was started by Merton Parks in 1953. Yellowstone National Park Heritage and Research Center, which opened May 18, 2005, is located in Gardiner and houses National Park Service archives, Yellowstone museum collections and reference libraries.