Byrne is best known for his work in TV's "In Treatment," as well as the films "Vanity Fair," "The Usual Suspects," "Millers Crossing," "Stigmata" and "Little Women."
He will play 8th century ruler Earl Haraldson in "Vikings," set to premiere in 2013, the History channel's president and general manager, Nancy Dubuc, said Monday.
The show will chronicle "the extraordinary and ferocious world of the mighty Norsemen who raided, traded and explored during medieval times," a synopsis said.
Co-starring George Blagden, the series will be filmed at Ashford Studios, a newly built facility in Ireland. All post-production, visual effects, sound design and music composition will take place in Canada.