The Stygnidae are a family of neotropical harvestmen within the suborder Laniatores.

The name of the type genus is derived from Ancient Greek stygnos "diabolic being".

Some Heterostygninae have white patches, stripes or spots on the dorsal scutum.

[1] The Heterostygninae are found in the Lesser Antilles, Nomoclastinae are endemic to Colombia, and the Stygninae live from north of the Tropic of Capricorn (central South America).

[1] The Stygnidae are sister to Cosmetidae and Gonyleptidae, and belong to the same group inside Gonyleptoidea as these and Cranaidae and Manaosbiidae.