| Lappajärvi | |
| Official Name: | Finnish: Lappajärven kunta Swedish: Lappajärvi kommun |
| Settlement Type: | Municipality |
| Coordinates: | 63.2167°N 61°W |
| Subdivision Type: | Country |
| Subdivision Name: |  Finland |
| Subdivision Type1: | Region |
| Subdivision Name1: | Southern Ostrobothnia |
| Subdivision Type2: | Sub-region |
| Subdivision Name2: | Järviseutu sub-region |
| Leader Title: | Municipal manager |
| Leader Name: | Sami Alasara |
| Established Title: | Charter |
| Established Date: | 1865 |
| Timezone: | EET |
| Utc Offset: | +02:00 |
| Timezone Dst: | EEST |
| Utc Offset Dst: | +03:00 |
Lappajärvi is a municipality in Finland in Southern Ostrobothnia region. It is from Lappajärvi to Seinäjoki, to Kokkola and to Vaasa. The municipality has a population of and covers an area of NaNLappajärvi}} of which NaNLappajärvi}} is water. The population density isNaNLappajärvi.
The municipality is unilingually Finnish.
Lake Lappajärvi, which gives the name to the municipality, is a meteor crater, one of the few meteor crater lakes found in Finland.
Singer and performer, Timo Kotipelto from the worldwide known Finnish power metal band Stratovarius was born and raised in Lappajärvi.