Iitti (Finnish: [ˈiːtːi]; Swedish: Itis) 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 6,433 (31 August 2024) 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 10.91 inhabitants per square kilometre (28.3/sq mi). Neighbour municipalities are Heinola, Kouvola, Lapinjärvi, Lahti and Orimattila. The municipality is unilingually Finnish.
The current administrative center of Iitti is in the village of Kausala. In 1990, the historical center of Iitti, which surrounds the old parish church, was voted the most attractive kirkonkylä ("church village") in Finland.
In the coat of arms of Iitti, the gray wavy fess refers to Kymi River and the key above it to the municipality's central position along the river. The coat of arms was designed by heraldist Ahti Hammar, and was officially confirmed for use on 3 March 1953.
The Kymi Ring motor sport center is located in Iitti, right next to the border of Kouvola.
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