| Lapinjärvi | |
| Official Name: | Finnish: Lapinjärven kunta Swedish: Lappträsks kommun |
| Native Name: | Finnish: Lapinjärvi – Swedish: Lappträsk |
| Settlement Type: | Municipality |
| Coordinates: | 60.6167°N 38°W |
| Subdivision Type: | Country |
| Subdivision Name: |  Finland |
| Subdivision Type1: | Region |
| Subdivision Name1: | Uusimaa |
| Subdivision Type2: | Sub-region |
| Subdivision Name2: | Loviisa sub-region |
| Seat: | Lapinjärvi (Kirkonkylä) |
| Leader Title: | Municipal manager |
| Leader Name: | Christian Sjöstrand |
| Established Title: | Charter |
| Established Date: | 1575 |
| Blank3 Name: | Climate |
| Blank3 Info: | Dfb |
| Timezone: | EET |
| Utc Offset: | +02:00 |
| Timezone Dst: | EEST |
| Utc Offset Dst: | +03:00 |
| Website: | www.lapinjarvi.fi |
Lapinjärvi (in Finnish pronounced as /ˈlapinˌjærʋi/; Swedish: Lappträsk) is a municipality in Finland, located in the southern interior of the country. Lapinjärvi is situated in the eastern part of the Uusimaa region. The population of Lapinjärvi is approximately, while the sub-region has a population of approximately . It is the most populous municipality in Finland.
Lapinjärvi covers an area of NaNLapinjärvi}} ofwhich NaNLapinjärvi}}is water. The population density isNaNLapinjärvi.
Neighbouring municipalities are Iitti, Kouvola, Loviisa, Myrskylä and Orimattila.
Lapinjärvi is a bilingual municipality with Finnish and Swedish as its official languages. The population consists of Finnish speakers, Swedish speakers, and speakers of other languages.
Lapinjärvi lake is located near the administrative village center in Lapinjärvi.
Results of the 2011 Finnish parliamentary election in Lapinjärvi: