Events from the year 1778 in Ireland.

• Monarch: George III

• 28 March – Hugh O'Reilly succeeds Daniel O'Reilly as Roman Catholic Bishop of Clogher, an office he will hold until 1801.^[1]
• April – the Ladies of Llangollen run away from Ireland to set up a rural household together.
• 24 April – American Revolutionary War: North Channel Naval Duel: John Paul Jones in USS Ranger captures HMS Drake in the North Channel off Carrickfergus.
• Papists Act provides a measure of Catholic Relief: Catholics now have property rights and may intermarry; and restoration of Catholic religious institutions begins.
• Charles Vallancey surveys West Cork.

• 4 March – Robert Emmet, nationalist, rebel against British rule in 1803 (executed 1803).
• 18 May – Charles Stewart, 3rd Marquess of Londonderry, soldier, politician and nobleman (died 1854).
• 29 September – Catherine McAuley, nun (died 1841).
• 15 November – George Canning, 1st Baron Garvagh, politician (died 1840).

• March – Thomas Roberts, landscape painter (born 1748).
• 28 March – Daniel O’Reilly, Roman Catholic Bishop of Clogher (born 1700).