The Oscar-nominated actor takes the leading role of the Shakespearean anti-hero in the big-screen adaptation, which also marks his debut as a director.
"I was a bit mad to be in it and direct it - but no-one else was clamouring to direct it," he said at the BFI London Film Festival.
Fiennes, 48, said he had a fascination with the play, having portrayed tragic dictator Coriolanus in Jonathan Kent's theatre productions in London and New York in 2000.
"I became obsessed with Coriolanus, having played him on stage about 10 years ago," he continued.
"I like its confrontational tone, I like how it confronts the audience with its questions about loyalty and political intrigue. It challenges and provokes audiences and is continually relevant."
His film, which also stars Vanessa Redgrave, Gerard Butler and Brian Cox, was shot in Serbian capital Belgrade within eight weeks.
"If I was to do it again, I would take more time. The time pressure made it doubly hard and at times, we were racing to finish," he said.
Fiennes, who is famed for his roles in Schindler's List, The English Patient and Harry Potter, admitted it was an unforgettable experience. "I hesitate to use the word 'fun'. It was nervy and adrenalised but it's exhilarating," added Fiennes.
Coriolanus, which will premiere as part of the BFI London Film Festival, opens in cinemas on January 20, 2012. See the trailer below...