Beef Steak

I'm trying to find the name of a thick steak, cut from a beef fillet, which ( depending which story you believe! ) derived its name from the noble title of a French aristocrat or from the name of the restaurant where the dish was invented by the resident chef.

Any thoughts?

Thanks for any offers :-)

Could it be 'Chateaubriand'? (I think that's the way it's spelt!)