The pair follow in the footsteps of Lord Richard Attenborough, Sir Michael Caine, Clint Eastwood and Dame Maggie Smith in receiving the honour.
Cronenberg, famous for his shocking films including The Fly and Crash, is the first Canadian to be awarded the fellowship, and is thrilled to be recognised by the British movie industry.
He says, "British cinema has been a potent inspiration for me and to be associated with this particular group of filmmakers is tremendously exhilarating.
"This is a monumental, in fact overwhelming, honour, and my being the first Canadian to receive it makes it all the sweeter."
Fiennes added he is "extremely honoured and delighted" to be made a BFI fellow.
The prizegiving will take place on 26 October (11) during the London Film Festival's 2011 awards ceremony.