A capping head for applying caps on containers or bottles and a capping assembly are provided. The capping head comprises a gripping assembly having a hollow body longitudinally extending along a vertical axis and internally defining a seat for the cap, the seat being delimited at its lower end by an inlet mouth for the introduction of the cap. A moving assembly is connected to the gripping assembly for controlling the movements thereof and is hermetically separated therefrom, and an ejector member is housed inside the hollow body of the gripping assembly, in such a manner that it is free to axially slide. The ejector member carries first and second magnetic elements such that a relative axial approach of the second magnetic element towards the first magnetic element results in a translation of the ejector member towards the lower inlet mouth of the gripping assembly.