Isojärvi National Park (Finnish: Isojärven kansallispuisto) is a national park in Central Finland. It covers 19 square kilometers (7.3 square miles) and was created in 1982. The landscape changes in elevation, and the area is covered with Scots pine and Norway spruce forests, as well as bogs. Signs of early human settlement and farming have been found in the region. The park is named after Lake Isojärvi, which is nearby.

There are two nature trails marked with red paint and several ring trails marked with blue paint. Most trails begin at the Heretty or Kalalahti parking areas. The trails range in length from 3.5 kilometers to 20 kilometers and vary in difficulty. The park has over 30 kilometers of trails, making it one of the largest parks in the region.