Palus Epidemiarum /ˈpeɪləs ɛpɪdiːmiˈɛərəm/ (Latin palūs epidēmiārum Marsh of Epidemics) is a small lunar mare in the southwestern part of the Moon's near side.

This feature forms a rough band of lava-flooded terrain that runs generally west–east, with a northward extension near the western end.

The northern extension of the mare reaches the outer rims of the crater pair Campanus and Mercator.

A narrow valley between these craters joins Palus Epidemiarum with Mare Nubium, and a rille from the Rimae Ramsden follows the course of this cleft.

The small double-walled crater Marth lies at the southern midpoint of this northern extension.