In an MMA fight it's mandatory to wear a cup/groin protector if you're a male. When you're training it's not necessary, but for sparring you'll want to wear one.
Diamond MMA makes by far the best cup you can buy for mixed martial arts. They have a jock strap, a cup and compression shorts but you can just by one product and get it all-in-one.
You can buy the compression shorts that come with a pocket for your cup and a built in jockstrap and the cup will come in the box with the rest.
The Diamond MMA Compression shorts are made with military grade elastics and premium spandex. It has a 4 strap jock strap system so that the cup fits perfectly in the pocket and fits great. Like other MMA shorts they have a drawstring for a good custom fit.
The Athletic cup has a elastomer design and the core is polycarbonate which gives maximum protections and comfort for the fighter. It's so comfortable because the edge is soft but it's very protective because it's made of the same material as bullet proof glass.
This cup was designed by award winning designers and engineers from Stanford. It's been supported by doctors and urologists as the best cup that can be found today.