I just bought a sigma 24mm super wide ii lens and it doesn t fit on my canon 7d what lens adapter would I need to get it on ?

Sigma are a 3rd party lens manufacturer who make lenses to fit different cameras. The adapter you need depends on which of the many available mounts your lens has.

Use of an adaptor is rarely a good idea. You loose AF and aperture control and may lose infinity focus. Return the lens and buy the model with the Canon EF mount.

Sigma 24mm f/1.4 DG HSM? It comes in 3 different mounts - Canon EF, Nikon F, and Sigma SA. Don't use an adapter.

Return the one you have to the store at once with the box and everything that came in it including the sales receipt and have it replaced with a Canon version. If you bought this online, contact the seller first before sending it over. You will have to pay for shipping both ways - back to the seller and for the replacement to you.

adapter you need depends on which of the many available mounts your lens has. Use of an adaptor is rarely a good idea. You loose AF and aperture control and may lose infinity focus. Return the lens and buy the model with the Canon EF mount.

So you truly do not know that you have to buy a Sigma lens that is MADE TO FIT a Canon camera? The thought of using an adaptor is ridiculous.

Using an adaptor is like trying to use a device from many years ago, with much lower image quality, and less than half the practicality of using the proper lens with your camera.

Get the lens exchanged, and state the exact model of the camera you want the exchanged lens to fit on. If you bought the lens second-hand, return it and get the refund. Then start again with the knowledge that you must buy a lens made to work on your camera.

Did you buy the proper Canon mount? If so, it might be meant for full frame Canon, you have a crop sensor camera. Also, an adapter won't really work. adapters work for mirrorless cameras, not so much for dSLRs with the extra distance of the mirror box area. returning or selling this item might be your only option, without having more detail.

You should've specified Canon mount !

Exchange it for one with a Canon mount.