Events from the year 1599 in Ireland.

• Monarch: Elizabeth I

• March 12 – Robert Devereux, 2nd Earl of Essex, is appointed Lord Lieutenant of Ireland by Queen Elizabeth I of England.
• March 27 – Essex leaves London with a large force to pursue a military campaign in Ireland.
• May 29 – Nine Years' War: Essex captures Cahir Castle in Munster.
• August 15 – Nine Years' War: Irish victory over the English at the Battle of Curlew Pass.
• September 8 – Essex in Ireland: Essex signs a truce with Hugh O'Neill, then leaves Ireland against the instructions of Queen Elizabeth.^[1]

• April 17 – Patrick Fleming, Franciscan ecclesiastical scholar (d. 1631)
• Probable date – John Lynch (Gratianus Lucius), Roman Catholic priest and historian (d. c.1677)
• Brian O'Rourke, son of Tadhg O'Rourke of West Breifne and Mary O'Donnell of Tyrconnell. Died in the Tower of London in 1641.

• January 19 – Richard Bingham, Marshal of Ireland, dies upon arrival in Dublin
• August 15 – Conyers Clifford, English commander, killed at Curlew Pass
• December 14 – Joan Boyle, first wife of Richard Boyle, 1st Earl of Cork, in childbirth (b. 1578)
• December 31 – John Houling, Jesuit, of plague in Lisbon, (b. c.1539)