In mathematics, an unfoldable cardinal is a certain kind of large cardinal number.

Formally, a cardinal number κ is λ-unfoldable iff for every model M of cardinality κ of ZFC-minus-power set, such that κ ∈ M, there is a non-trivial elementary embedding j of M into a transitive model with the critical point of j being κ and j(κ) ≥ λ.

A cardinal is unfoldable iff it is λ-unfoldable for all ordinals λ.