The present disclosure relates to semiconductor structures and, more particularly, to high voltage diode structures and methods of manufacture. The structure includes: a diode structure composed of first well of a first dopant type in a substrate; and a well ring structure of the first dopant type in the substrate which completely surrounds the first well of the first dopant type, and spaced a distance “x” from the first well to cut a leakage path to a shallower second well of a second dopant type.