An igniter, such as a corona igniter for an internal combustion engine, and a method of manufacturing the igniter, are provided. The igniter includes an insulator with enlarged upper and lower end regions extending axially beyond opposite ends of a constrained, reduced diameter region of a shell through passage. The enlarged lower end region of the insulator is disposed axially outwardly of a lower end of the shell. The insulator is hermetically sealed to the shell and is permanently fixed against being removed axially outwardly from the shell. The method can include conforming the shell to the contour of the insulator by plastically deforming the shell, or casting the shell about the insulator. Alternatively, separate pieces of metal can be disposed around the insulator to form the shell which is conformed to the insulator.