2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/145356The celebrated Kadison--Sakai theorem states that every derivation on a von Neumann algebra is inner. In this paper, we prove this theorem for ultraweakly continuous *-σ-derivations, where σis an ultraweakly continuous surjective *-linear mapping. We decompose a $σ$-derivation into a sum of an inner σ-derivation and a multiple of a homomorphism. The so-called *-(σ,τ)-derivations are also discussed.10 pages, completely revisedFunctional AnalysisOperator Algebras46L57 (Primary) 46L05, 47B47 (Secondary)text