The OnePlus 3 and OnePlus 3T are really nice-looking phones, so you'll want any case you put on it to look just as good (or better). Of course, the best OnePlus 3 cases should also be functional, keeping your phone safe from butterfingers, or maybe even protecting against the odd bump or drop.
LK's clear silicone case lets you show off the OnePlus' design, while its raised lips and borders shield the camera and screen from damage. It's a slim case, too, so it won't add too much bulk to the device.
If you're looking for a case that's a little more rugged, OtterBox's custom-designed case for the OnePlus 3/3T is just what you need. It protects your phone from bumps and drops thanks to a hard outer layer and soft, shock-absorbing silicone interior. Plus, it looks really modern for a case that protects your device from everything life throws at it.
Another great option is OPdenk's leather flip cover. It's available in a variety of colors and feels and looks amazing. It has a slot on the back you can use to store a couple of credit cards or IDs, as well as a kickstand to prop up your device while watching a video or movie.
If you're not satisfied with OnePlus' grippy sandstone finish, you can always get something similar on their official case. It's a clip-on case that provides corner and edge protection for your device, while it comes in a range of different finishes from bamboo to the company's traditional grippy sandstone (and even carbon fibre). It's also waterproof and has cutouts for ports, speakers and cameras.
