Skein may refer to:
A traditional English collective noun for a flock of wildfowl such as ducks, geese, or swans in flight A wound ball of yarn with a center-pull strand: see hank A metal sleeve fitted over the end of a wagon axle, to which the wheel is mounted Skein dubh or sgian-dubh, a Scottish knife Skein (unit), a unit of length used by weavers and tailors
Fiction Skein (character), a Marvel Comics supervillain
Mathematics Skein (graph theory), a subgraph of a graph formed by paths connecting a given pair of vertices Skein (hash function), a cryptographic hash function submitted to the NIST competition Skein module, a mathematical structure used in knot theory Skein relation, a key identity used to define knot polynomials
See also Skien (disambiguation)