The name velvet spider describes the dark and shiny appearance of members of the family Eresidae. Some species also have brightly-colored highlights, such as the red, white, and black ladybird spiders of Europe and North Asia. This family also includes some of the world?s most cooperative spider species. Social species can be very abundant in parts of tropical Africa and Asia with conspicuous colonies dotting the landscape. Social colonies may consist of hundreds of closely-related individuals that participate in dramatic mass attacks on prey and care for their young. The ecology of these social species is fascinating and has been the subject of several landmark scientific papers. By contrast, most kinds of velvet spider are rarely encountered. Most species keep well hidden or dig burrows and live underground. This monograph provides a generic-level review of Eresidae documented with collections of photographs, scanning electron micrographs, and illustrations. A key to the nine genera and other major lineages is provided. A new phylogeny of Eresidae based on molecular sequence data expands on a previously published analysis. Cybertaxonomic enhancements include an interactive map of the specimens used in the study explorable using Google Earth, specimen records uploaded to GBIF, and molecular sequence alignments and other data archived on Dryad. An EDIT Integrated Research grant provided principal funding for this project.