Hartola is a municipality of Finland. It is located in the Itä-Häme, Päijänne Tavastia region. The municipality has a population of 2,660 (31 December 2020), which make it the smallest municipality in Päijänne Tavastia in terms of population. It covers an area of 675.38 square kilometres (260.77 sq mi) of which 132.18 km² (51.03 sq mi) is water. The population density is 4.9 inhabitants per square kilometre (13/sq mi). Neighouring municipalities are Heinola, Joutsa, Luhanka, Pertunmaa and Sysmä.

The municipality is unilingually Finnish. The municipality is also known as "Gustav Adolfs" in Swedish. Hartola is home to the Itä-Hämeen Museo, the regional museum for seven municipalities.

Since 1987, the town has billed itself as a sovereign royal parish based upon a 1784 proclamation by King Gustav III of Sweden creating a new parish on the eastern border of his kingdom in honor of his son, Gustav Adolf.

At every first Saturday in September, there is a fair at Hartola. The event is biggest in Finland at its genre.

Municipality is also known about writer Maila Talvio's place of birth.