Zalma, once known as Bollinger's Mill, is a town on the banks of the winding Castor River at a point where the river makes a horseshoe bend in southern Bollinger County in southeast Missouri. When the railroad moved to town, the name Bollinger's Mill was changed to Zalma, after railroad worker Zalma Block. Zalma is also said to come from a Native American word meaning "the end." As of the 2010 U.S. Census, Zalma had a population of 122.
Zalma is part of the Cape Girardeau−Jackson, MO-IL Metropolitan Statistical Area. Zalma is home to a number of state parks that feature a number of activities such as deer hunting, fishing, bird watching, horseback riding, and hiking. Blue Pond, the deepest natural pond in the state of Missouri, is located outside of Zalma.