Palmyra is a city in and the county seat of Marion County, Missouri, United States. The population was 3,467 at the 2000 census. It is part of the Hannibal Micropolitan Statistical Area.
Palmyra is located at 39°47′51″N 91°31′29″W / 39.7975°N 91.52472°W / 39.7975; -91.52472 (39.797396, -91.524857). According to the United States Census Bureau, the city has a total area of 2.2 square miles (5.7 km²), all land.
In 1862 the city was the scene of the Palmyra Massacre, in which ten Confederate prisoners were killed in retaliation for the disappearance of a local Union man.