Are all nikon lenses interchangeable?

I have a Nikon L320 and am looking for a fish eye lens to buy for it but they all say for d5100, d3100, etc. Will they still fit on my camera?

The L320 does not take interchangeable lenses.

No, only the Nikon 1 series EVIL models, and the D-series DSLRs take interchangeable lenses (and each series has different mounts).

Your L-series (like the P- and S- series) has a fixed lens.

The L320 is a low end bridge camera. The lens is built in and can't be changed.
The sell push on lens adapters, and they're junk not worth buying.

Yes, generally all Nikon "F-Mount" lenses are interchangeable. The problem is, not all cameras are compatible with those lenses.

This is the situation with the L320. It can't use those interchangeable lenses.

It is just a basic no-frills compact camera with a permanently attached lens.

Only DSLRs are compatible with Nikon F-Mount interchangeable lenses (cameras with a "D" prefix).

Nikon 1 cameras (cameras with a J or V prefix) are compatible with Nikon "CX" mount interchangeable lenses.

Nikon L, S, P, A, and AW (except the AW1) prefix cameras have fixed lenses and can't use interchangeable lenses. The only exception here is the P7xxx cameras… You can fit a lens adapter on these cameras and use auxiliary lenses (but still no fisheye).

No they won't because your camera has a fixed, built in lens. It's not interchangeable.