Acamptonectes is an extinct genus of ophthalmosaurid ichthyosaur known from England and Germany. It was collected from the Hauterivian stage of England and Germany and from the Cambridge Greensand Formation, eastern United Kingdom, dating to late Albian or early Cenomanian stage, of the Early Cretaceous-Late Cretaceous boundary. Acamptonectes was first described by Valentin Fischer, Michael W. Maisch, Darren Naish, Ralf Kosma, Jeff Liston, Ulrich Joger, Fritz J. Krüger, Judith Pardo Pérez, Jessica Tainsh and Robert M. Appleby in 2012 and the type species is Acamptonectes densus.