The all-star cast includes the two-time Oscar nominee in the title role alongside Vanessa Redgrave as his ambitious mother Volumnia and Gerald Butler as Tullus Aufidius, an enemy army commander.
Swapping swords and sandals for automatic weapons and mobile phones, the film borrows from present-day conflicts such as those in Afghanistan and Iraq by depicting a world power locked in combat with insurgents.
The picture's script was written by John Logan, the screenwriter of "Gladiator" and "The Aviator," and re-imagines one of Shakespeare's lesser-known plays as a contemporary look at the overreach of empires.
Fiennes, 48, said he had played the role in a London theatre 10 years ago and the wars of the last decade had underlined the relevance of the story.
"The idea of Coriolanus as a film was inside my head and heart for some time," he told reporters after a well-received press screening on Monday.
"All around me, even before 9/11 but certainly afterwards, I kept seeing images in newspapers and on television that seemed to come from this story. I felt more and more convinced that the world around us was the right setting for this piece."
Filmed in Belgrade, the picture shows Fiennes as a loyal warrior whose triumphs on the battlefield propel him toward a political career in Rome.
But he finds himself unable to adapt to the expectations of the angry citizens of the empire and is eventually banished. Isolated and humiliated, Coriolanus leaves his family behind and takes up arms with Aufidius.
But in the wrenching dramatic climax, his mother seeks him out at the rebel camp with a final plea for him to return home.
Redgrave, 74, said Volumnia was a challenge even for a seasoned actress. "I didn't think I could play her but thanks to the fact that Ralph is an extraordinary director, I had complete trust in him," she said.
"He assembled such a fantastic team of people, all of whom had trust in him and therefore we had trust in each other.
"For some reason, but basically for that reason, I felt that I could see my way to a woman who was prepared for her son to be killed rather than for him to lose his honour or his country. It's a concept that I think is very unfamiliar today except in military families."
Butler, best known for his roles in the blockbuster "300" and a string of romantic comedies, said he relished the chance to sink his teeth into Shakespeare.
"Something intellectual is always challenging for me," the 41-year-old joked.
"I wasn't somebody who was brought up steeped in Shakespeare. And to enter into this venture at such a high level with Ralph and Vanessa... was just amazing."
Fiennes said there was a clear homoerotic component in the relationship between Coriolanus and Aufidius which he and Butler consciously brought to the screen.
“The erotic element is very apparent in Shakespeare's story," he said.
"In the battle scene, the physical contact should be suggestive of some kind of love-making."
"Coriolanus" is one of 16 films in the running for the festival's Golden Bear top prize, to be awarded Saturday by a jury led by Italian-American actress and director Isabella Rossellini.
Other contenders include "Margin Call" starring Kevin Spacey and Demi Moore in a thriller about the start of the financial crisis and "Tales of the Night", a 3D animated feature by France's Michel Ocelot.