A high-voltage isolator is disclosed which has a first electrical connecting piece and a second electrical connecting piece, between which an electrical isolating body extends. The end sections of the connecting pieces are connected to the isolating body, with a toroidal field control element being arranged on at least one of the end sections. A slot, which extends in the circumferential direction of the end section, is introduced on the end section which has the field control element. The field control element and the respectively associated end section are formed integrally. As a result of the slot, tension and compression forces which occur during longitudinal and lateral contractions of the isolating body and act at right angles to the longitudinal axis of the end section can be largely prevented, as can shear forces, while at the same time achieving a high level of uniformity in an area of the isolating gap, for electrical fields which occur during operation.