Pernå (Finland Swedish: [ˈpæːrno], Sweden Swedish: [ˈpæ̌ːɳɔ]; Finnish: Pernaja) is a former municipality of Finland.

Pernå is located in the province of Southern Finland and was part of the Eastern Uusimaa region. The municipality had a population of 3,961 (31 December 2009) and covered an area of 1,107.07 square kilometres (427.44 sq mi) of which 687.6 km² (265.5 sq mi) is water. The population density was 9.44 inhabitants per square kilometre (24.4/sq mi).

The municipality was bilingual, with the majority being Swedish and minority Finnish speakers.

Pernå is the oldest municipality in the Eastern Uusimaa region. The current municipalities of Lapinjärvi, Liljendal and Loviisa were originally part of it. Mikael Agricola, the founder of written Finnish was born in Pernå in the early 16th century. He is also considered to be the "Reformator of Finland" in the transfer from Catholicism to Lutheranism.

Situated conveniently by the coast, and engulfing also a small river, the lands of Pernå were attractive at a time when waterways rather than proper roads provided the means of transport. There are a number of manor houses in the Pernå area - most notably Sarvlaks manor, which dates back to the 1450s - at a time when Finland was a part of Sweden.

The origin of the name "Pernå" is uncertain; some think it links with the Uralic word "Pern" meaning lime- or lindentree. "Å" is Swedish for a small river, i.e. the name then being Lindenriver if translated.

On January 1, 2010, Pernå was amalgamated with Loviisa, Ruotsinpyhtää and Liljendal to form a new municipality of Loviisa.