Gardiner is a census-designated place (CDP) in Park County, Montana, United States,[1] along the 45th parallel.

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.

[6] The name Gardiner derives from Johnson Gardner, a fur trapper who operated in the area in 1830–31.

In 1870, when the Washburn–Langford–Doane Expedition passed through the area they began calling the river Gardiner, a phonetic error.

[8] When the Hayden Geological Survey of 1871 passed through the Gardiner area, they encountered two men, named J.C. McCartney and H. R. Horr, who had laid claim to 320 acres (1.3 km2) and established a ranch and a bath house on the Mammoth terraces near Liberty Cap.

On February 9, 1880, a territorial post office was established just outside the park boundary and Gardiner, Montana began.

[8] In 1883, the Northern Pacific Railway completed the extension of their Park Branch Line from Livingston, Montana to Cinnabar north of Gardiner.

For statistical purposes, the United States Census Bureau has defined Gardiner as a census-designated place (CDP).