Tony O'Reilly was born in Dublin. He was educated at Belvedere College and went on to study law at University College Dublin. An excellent rugby player he played as winger for the British Lions on their 1955 tour of South Africa and the 1959 tour of Australia and New Zealand. He also played for Ireland, earning 28 caps between 1955 and 1963, with a surprise 29th cap in 1970.
He went to work for a consultancy company and then an Irish firm selling agricultural products. He earned his Ph.D from the University of Bradford in agricultural marketing. He joined An Bord Bainne (the Irish Dairy Board) in 1962 as CEO, where he developed the Kerrygold brand. In 1966 he became head of the Irish Sugar Company.
O'Reilly made his name in international business at H. J. Heinz & Co He joined the company in 1969 to become MD of the Heinz subsidiary in England. He moved to the company HQ in Pittsburgh in 1971 when he was promoted to Senior Vice President. In 1973, he became COO and President. He continued his rise and became CEO in 1979 and Chairman in 1987 succeeding Henry John Heinz II, the first non-Heinz family member to hold that post. His guidance helped transform the company into an major international competitor, increasing the company's value fifteen fold. O'Reilly left Heinz in 1998 in response to shareholder pressure, he was replaced with William R. Johnson. It is reported that O'Reilly still has a 2% shareholding in Heinz.
O'Reilly had bought into Independent Newspapers, a Dublin-based company, in 1973, he currently holds a 29% stake. He pushed the company to expand into other national markets and to increase its reach in Ireland. Throughout the 1990s INM bought into South Africa (from 1994), Australia (from 1987) and New Zealand (from 1995). Acquiring 38 newspaper titles, over 70 radio stations, cable and telecoms interests at a cost of around €1.3 billion. In Britain, INM expanded its interests, taking control of the national broadsheet The Independent in 1995, edging out MGN and Prisa. The company has around 200 national and regional titles in total. In 2002 INM had revenues of €1.3 billion and profits of €223.2 million. The group has debts in the region of €1 billion.
O'Reilly also has interests in Fitzwilton, a holding company, with a 40% share in Waterford Wedgewood. He is also part of the Valentia consortium, which bought into Eircom in 2001.
He was knighted by the British in the 2001 New Year's Honours, with the approval of the Irish government, in recognition for his work as head of The Ireland Funds charity.
He is married to Chryss Goulandris, a Greek shipping heiress.