Mäntsälä

(31 December 2025) and covers an area of 596.11 square kilometres (230.16 sq mi) of

which 15.26 km2 (5.89 sq mi)

is water. The population density is

35.91 inhabitants per square kilometre (93.0/sq mi). The municipality is unilingually Finnish. Mäntsälä is one of three municipalities in the Uusimaa region that do not have a Swedish name; the others are Nurmijärvi and Askola.

Mäntsälä lies about 60 kilometres (40 mi) north of Helsinki, the capital of Finland. During the last few years, the population of Mäntsälä has been one of the most rapidly increasing in Finland. A new railway, the Kerava–Lahti railway line, was built between Kerava and Lahti with passenger traffic starting on 4 September 2006 from Mäntsälä railway station. Helsinki is about 40 minutes away, and Lahti even closer. Highway 4 (E75) connecting both cities passes through Mäntsälä.

The coat of arms of Mäntsälä has its theme in the region's traditional livelihoods; the head of the moose refers to the hunting lands of the region, and the clovers symbolizes local agriculture. The coat of arms was designed by Olof Eriksson and approved by the Mäntsälä Municipal Council on 16 December 1950. The coat of arms was officially approved by the Ministry of the Interior on 20 February 1951.