2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/59437We generalize the hyperkaehler quotient construction to the situation where there is no group action preserving the hyperkaehler structure but for each complex structure there is an action of a complex group preserving the corresponding complex symplectic structure. Many (known and new) hyperkaehler manifolds arise as quotients in this setting. For example, all hyperkaehler structures on semisimple coadjoint orbits of a complex semisimple Lie group $G$ arise as such quotients of $T^*G$. The generalized Legendre transform construction of Lindstroem and Rocek is also explained in this framework.Differential Geometry53C26text