A high-voltage insulator includes a metal armature, an insulating tube joined to the metal armature, which is adhesively bonded to the metal armature at an end formed as a supporting ring, and an axially symmetrical adhesive-bonding joint disposed around the axis of the insulating tube. An annular grove, which is formed in the metal armature, is disposed around the axis of the insulating tube and receives an end portion of the supporting ring. Sealing surfaces are respectively formed in the groove and in the supporting ring. The sealing surfaces are arranged and formed in such a way that, when the insulating tube and the metal armature are joined, they slide on one another, thereby forming a seal, and the supporting ring acting as a displacement body presses adhesive that has been introduced into the groove before the joining into the adhesive-bonding joint.