Grindstone Lake is a large freshwater lake located in Dell Grove Township, Pine County, in east-central Minnesota approximately 6.5 miles (10.5 km) west of Sandstone, Minnesota.

The lake is roughly oval shaped being approximately 2 miles (3.2 km) in length north to south and 0.5 miles (0.80 km) east to west, and a maximum depth of 153 feet (47 m).

The lake has several small streams that drain the area wetlands and is considered the headwater for the Grindstone River.

Sandstone taken from near the lake was used to make sharpening stones.

It also features a sea plane base, a religious summer camp, and a nature education center.