The Irish are a minority gang in Oz as few members of this gang are shown in show. They are led undisputedly by Ryan O'Reily throughout the show.
The Irish tend to ally with The Homeboys and The Italians for drug trade on various occasion, but behind their back, Ryan manipulates them to go against each other. They also have 2 dirty COs working for them: Mike Healy in season 1 and Claire Howell for a brief time in season 4.
- Episode 1.1 "The Routine" - Ryan O'Reily arrives in Oz and is plotting revenge against Italian inmate, Dino Ortolani for shooting him. O'Reily ask Jefferson Keane, leader of the Homeboys if he could take care of Ortolani for him. But Keane tells him they don't kill wise guys. However, this changes after Ortolani puts a severe beating on his gay brother, Billie Keane. Keane orders Johnny Post to kill Ortolani when the time is right. Later, O'Reily taunts Ortolani for not killing him and tells him he's coming to Em City. Ortolani retaliates by beating up O'Reily and almost drowning his head in the toilet. Afterwards, Ortolani suffocates AIDS patient, Emilio Sanchez. Ortolani is beaten senseless by the COS and is taken to the hole, sedated for his violent temper. O'Reily uses his CO connections to let Post in the hole. Post pours flammable liquid on the sedated Ortolani and sets him on fire.
- Episode 1.2 "Conjugals, Visits, and Otherwise" - Ryan arrives in Em City and is sponsored by Vern Schillinger. Later O'Reily tries to get Keane to betray Post but refuses O'Reily as Keane would never rat on one of his own. Schibetta orders Burrano to make Ryan give up the guy who wasted Ortolani. Ryan rats on Johnny Post to Nino Schibetta. As a result, Post is castrated and murdered by the Italians.
- Episode 1.3 "God's Chillin" - O'Reily meets Beecher and asks him if he could assist him with his appeal since his lawyer did a terrible job with his case. O'Reily also becomes Beecher's drug supplier and they both get high. Later, O'Reily takes help of Mike Healy to warn Jefferson Keane about no harm coming to him. Keane however becomes a Muslim and tries to convince O'Reily to turn himself in for Post's murder. O'Reily treating what Keane says to him as a threat, plans to set him up. Later on, O'Reily's plan is in motion. Keane is taken to the gym where he faces off against two Latinos and kills one of them in self defense. Healy and the COs are spotted by Keane with cameras. Keane is set up and is planned to be executed.
- Episode 1.4 "Capital P" - Jefferson Keane is put on Death Row and is executed by lethal injection. Ryan and Joey D'Angelo argue over a bet which almost leads to a fight. O'Reily then lies to the Homeboys and tells them that Joey D'Angelo was the one who set up Keane. The Homeboys ambush D'Angelo in the kitchen and as result D'Angelo is in the infirmary. With Joey out of commission, O'Reily offers to help Nino anyway he can. Nino accepts his help and becomes his new partner.
- Episode 1.5 "Straight Life" - Nino tells Ryan to shut down Healy's operation as it is cutting into his profits. Ryan gets Healy busted and is sent to the hole for a solid month.
- Episode 1.6 "To Your Health" - O'Reily and Nino seem to be getting along well. Nino has Ryan run the kitchen as he thinks Adebisi is unfit for the job. This angers Adebisi and he has the Homeboys not listen to O'Reily. O'Reily knowing that Nino is trying to get the two to go at eachother's throats, has an idea. Ryan and Simon Adebisi scheme to have Nino Schibetta killed and take over his drug business. They start putting glass into his food.
- Episode 1.7 "Plan B" -
- 'episode 2.2' - Ryan discovers he has breast cancer.
- 'episode 2.4' - Ryan begins to heal after he survives the lumpectomy.
- 'episode 2.5' - Cyril O'Reily comes to visit Ryan and Ryan asks him to murder Preston Nathan, Gloria Nathan's husband.
- 'episode 2.7' - Cyril arrives to Oz and stays in Unit B, where he is raped by Vernon Schillinger and The Aryans.
- 'episode 2.8' - Ryan donates blood to Eugene Rivera, and McManus in return transfers Cyril to Emerald City.
Their most notable drug dealers and soldiers are: Cyril O'Reily, Timmy Kirk, Padraig Connolly, Liam Meaney and Patrick Keenan.
Ryan O'Reily - Leader 1997-2003
Characters murdered in Oz by The IrishEdit
- Nino Schibetta: Poisoned with ground up glass by Ryan O'Reily and Simon Adebisi. (1997)
- Hamid Khan: Accidentally killed in a boxing tournament by Cyril O'Reily. (2000)
- Patrick Keenan: Had his head bashed with a weight in the gym by Ryan O'Reily. (2000)
- Supreme Allah: Poisoned with eggs that Poet and Ryan put in his food, with help from Augustus Hill. (2001)
- Li Chen: Stabbed twice in the heart by Cyril O'Reily for saying he will rape Ryan's mother. (2002)