Michael O'Leary was born 20 March 1961, the second in a family of six, in Mullingar in Westmeath.[3] He was educated at Clongowes Wood College, County Kildare. In 1979 he began a four-year Bachelor in Economic and Social Studies programme at Trinity College. He graduated from Trinity and then worked as a trainee with Stokes Kennedy Crowley (later known as KPMG), studying the Irish tax system. He left after two years in 1985, setting up profitable newsagents in Walkinstown and Terenure, Dublin.
While at Stokes Kennedy Crowley, O'Leary met Tony Ryan, head of GPA (Guinness Peat Aviation, a leasing company). Ryan was one of the firm's clients and O'Leary advised Ryan on his personal income tax affairs. In 1987, he then hired O'Leary as his personal financial and tax advisor, where Ryan's main interest was in GPA. Ryanair was established around this time and originally followed a traditional business model, but quickly began to lose money. Subsequently O'Leary was sent to the USA to study the novel Southwest Airlines business model.