Ryan O'Reily is the deuteragonist and primary Irish inmate featured in Oz. Portrayed by Dean Winters.
- "Prisoner number 97P904, Ryan O'Reily. Convicted July 12, '97 - Two counts of vehicular manslaughter, five counts of reckless endangerment, possession of a controlled substance, criminal possession of a weapon, parole violation. Sentence: Life imprisonment, up for parole in 12 years."
O’Reily is an Irish American hoodlum originally sentenced to 12 years to life for killing two people while driving under the influence of drugs and alcohol, then 40 to life after confessing to a murder he had his brother, Cyril, commit. Before he was arrested for his original crime he was running a street gang of Irish American hoodlums called The Bridge Street Gang , with Cyril as his lieutenant/bodyguard. When his brother is permanently brain-damaged in a fight with a rival at a funeral, Ryan, blaming himself, goes on a drug and alcohol-fueled rampage throughout the city.
Highly intelligent and completely ruthless, O'Reily survives in Oz by manipulating everyone around him, and working with the most dangerous inmates using a variety of inmate gangs to get whatever he wants; series creator Tom Fontana has likened him to Iago, the villain of Shakespeare's Othello.
Ryan is extremely protective of his brother Cyril, and has no qualms with striking against anyone who threatens him, including guards. Above all else, Ryan strives to keep Cyril in Em City where Ryan can defend him. Cyril in turn cares about Ryan and depends on him a great deal, usually obeying him, which has led to Ryan taking advantage of him more than once.