Glen St. Mary is a town in Baker County, Florida, United States.

According to the United States Census Bureau, the town has a total area of 0.4 square miles (1.0 km2), all land.

The climate in this area is characterized by hot, humid summers and generally mild winters.

As of the 2020 United States census, there were 463 people, 238 households, and 162 families residing in the town.

[14] As of the 2010 United States census, there were 437 people, 203 households, and 163 families residing in the town.