Is Nikon D800 and Canon EF 400mm f/2,8 L IS II USM compatible?

Below you will find your chosen camera and lens. Click on the product name for more information.

Buy	Nikon D800 Released: 2012 Type: Digital SLR Sensor: FX (Full frame) 36,3 Megapixels 7360 x 4912 pixels
Buy	Canon EF 400mm f/2,8 L IS II USM Released: 2010 Telephoto Lens (prime) Focal Length: 400 mm Aperture: f/2,8

Can you combine these two?

This is the short answer:

No! This combination is not compatible

The camera and lens you have chosen cannot be combined. Here is a longer answer:

A non-Nikon lens on a Nikon camera

This is a Canon lens and unfortunately they are not constructed to work with Nikon cameras. If the lens would have been a Sigma, Tamron och Tokina it would perhaps be different since they are available with a compatible Nikon mount.