The Kerry-born star has teamed up with Northern Irish screenwriter Ronan Bennett to develop an epic about the mythical Irish hero.
Fassbender, who won an Ifta for his portrayal of a tortured sex addict in Shame, will play the lead role in the movie, which is still in development stage.
It is expected he will undergo a gruelling physical training regime to bulk up in order to portray the one-man fighting machine, who, according to folklore, had superhuman powers from his divine ancestry.
It is understood the epic’s plot will loosely follow The Táin, the central story of the Ulster cycle of ancient Irish tales in which the chariot-driving warrior, aged 17, single-handedly defends Ulster against the armies of Queen Méabh of Connacht.
Having shot to fame as IRA prisoner Bobby Sands in the 2008 film Hunger, the actor found global stardom more recently in Shame, which also earned him a best actor award at the Venice Film Festival.
The actor, based in London, showed his versatility in his latest film A Dangerous Method, in which he plays Swiss psychiatrist Carl Jung, while he has bagged another starring role in Prometheus, Ridley Scott’s prequel to his sci-fi classic Alien.
Fassbender is also making a third film with director Steven McQueen in Twelve Years a Slave.
He admits his workload means everything else comes second to filming.
“To be honest, relationships as a whole for me, in this industry, have been a difficult thing to maintain,” Fassbender said.
“I would be prepared to walk away from relationships because of my job. I wanted to give this everything and go for it 110%, so I guess my work has taken precedence over that.”