Monobia quadridens, also known as the four-toothed mason wasp, is a species of solitary potter wasp found in North America. It grows to a wingspan of 18 millimetres (0.71 in), and feeds on small caterpillars and pollen. There are two generations per year, with one generation overwintering as pupae. It nests in a variety of cavities including tunnels abandoned by carpenter bees, old nests built by mud daubers, and hollow plant stems.