Iitti is a municipality of Finland. It is located in the province of Southern Finland and is part of the Päijänne Tavastia region. The municipality has a population of 6,444 and covers an area of 687.09 square kilometres (265.29 sq mi) of which 97.27 km2 (37.56 sq mi) is water. The population density is 10.93 inhabitants per square kilometre (28.3/sq mi). Neighbour municipalities are Heinola, Kouvola, Lapinjärvi, Lahti and Orimattila. The municipality is unilingually Finnish.

Orimattila is a town in Päijänne Tavastia region, Finland. The southern part of Lahti is connected to the village of Orimattila, which is located in the region of Pennala. There are also several municipalities in the area, such as Iitti, Kärkölä, Lahti, Mäntsälä, and Pukkila.