Can I use a Nikon lens with my Canon camera?

I'm looking for a telephoto zoom lens for my Canon camera, does it have to be Canon too? Or can I choose another brand?

Nope, you can't use Nikon lenses on a Canon.

It is recommended that you stick with Canon brand lenses, everything that Nikon has, Canon has, and at about the same price. If you really want a nice lens, you can look at Zeiss optics, they make lenses with canon mounts.

All other third party lenses, you can use for sure you just need to buy a lens mount.

with that being said, you can't use nikon because they also have their own DSLR Cameras that they make their lenses for

No. Your choices are Canon lenses or 3rd party lenses (lenses made by Sigma, Tokina, Tamron, etc.) Quite often the 3rd party lens makers are more cost effective & made better than than the Camera makers lenses. I purchased a Tamron for my Canon & got a real nice lens for less than Canon's equivelent lens.

Adapter Ring you use Nikon lens with Canon see more http://www.onitsukathai.com/?s=Adapter+Ring&x=22&y=11

You can use any lens as long as it has the Canon EF mount. Nikon lenses do not. Aside from Canon, try Sigma and Tamron. Just make sure about the mount. Third-party lens makers make the same lens model for different camera mounts.