Blackduck is a city in Beltrami County, Minnesota, United States. The population was 785 as of the 2010 census.
According to the United States Census Bureau, the city has a total area of 1.5 square miles (4.0 km²), of which 1.5 square miles (3.9 km²) are land and 0.04 square mile (0.1 km²) (1.96%) is water.
As of the census of 2000, there were 696 people, 304 households, and 175 families residing in the city. The population density was 465.8 people per square mile (180.4/km²). There were 324 housing units at an average density of 216.8 per square mile (84.0/km²). The racial makeup of the city was 92.10% White, 0.86% African American, 3.45% Native American, 0.14% Asian, 0.14% from other races, and 3.30% from two or more races. Hispanic or Latino of any race were 0.72% of the population.