This thesis examines the history of the O’Donel estate in West Mayo, from the purchase of the estate by Sir Neal O’Donel in the late eighteenth century to the sale of most of the estate, in the 1850s in the Encumbered Estates Court, by his grandson Sir Richard Annesley O’Donel. The estate was purchased from John Thomas Medlicott and Thomas John Medlicott for £33,589 19s 4d, which was equal to nineteen years and a half purchase of the rental income minus the head rent amounting to £1722 11s 3d per year. 1 The O’Donels owned land in three baronies of Mayo, the Tarmon estate in the barony of Erris, the Cong estate in the barony of Kilmaine and the Newport estate in the barony of Burrishoole. Included in the sale of lands by the Medlicotts was also land in Counties Tipperary, Kilkenny and Waterford but this was probably disposed of almost immediately as the only reference to it in the O’Donel papers is in the deed of sale of 17 July 1774.