A mask and a method of manufacturing a mask assembly, the mask including a body, and the body including one end and another end facing each other in a length direction and having a first surface and a second surface facing each other in a thickness direction; and a pattern region between the one end and the other end, the pattern region including a plurality of pattern holes and a plurality of ribs between the plurality of pattern holes, wherein a curl value of the mask, which is defined as a shortest distance from a plane tangent to a center of the body to the one end or the other end of the body, is 1,000 μm to 4,000 μm.