Grantsburg is an unincorporated community and Census-designated place in Union Township, Crawford County, Indiana.
Grantsburg was laid out in 1854.
The Grantsburg post office (spelled Grantsburgh in early years) was established in 1854. John V. Grant was an early postmaster.
The United States Census Bureau delineated Grantsburg as a census designated place in the 2022 American Community Survey.