Muir is a village in Lyons Township, Ionia County in the U.S. state of Michigan. The population was 634 at the 2000 census.
According to the United States Census Bureau, the village has a total area of 0.8 square miles (2.0 km²), of which, 0.8 square miles (2.0 km²) of it is land and 1.30% is water.
As of the census of 2000, there were 634 people, 246 households, and 171 families residing in the village. The population density was 830.5 per square mile (322.1/km²). There were 264 housing units at an average density of 345.8 per square mile (134.1/km²). The racial makeup of the village was 96.06% White, 0.32% Native American, 0.95% from other races, and 2.68% from two or more races. Hispanic or Latino of any race were 2.37% of the population.