Events from the year 1670 in Ireland.

• Monarch: Charles II

• February–April – William Penn visits the Quaker William Morris at Castle Salem, Cork.
• March 7 – Oliver Plunkett, Roman Catholic Archbishop of Armagh and Primate of All Ireland, sets foot on Irish soil for the first time in 23 years.
• June 17 – Peter Talbot, Roman Catholic Archbishop of Dublin and Primate of Ireland, holds his first provincial synod in Dublin.^[1] It opens with Solemn High Mass, which for forty years many of the faithful have not witnessed. A subsequent assembly of the senior clergy produces a dispute over the Primacy of Ireland.
• Barrack Bridge is constructed over the River Liffey in Dublin.^[2]
• William Robinson is appointed Surveyor General of Ireland.
• First recognized precursor to modern Gaelic football is played in County Meath.^[3]

• December 26 – upper gallery of the Smock Alley Theatre in Dublin collapses for the first time.

• January 24 – William Congreve, English playwright (studies at Kilkenny School and Trinity College Dublin) (d. 1729)
• November 30 – John Toland, philosopher (d. 1722)
• Thomas Burgh, military engineer, architect and politician (d. 1730)
• Sir Pierce Butler, 4th Baronet, politician (d. 1732)
• Arthur Dillon, soldier in the French army (d. 1733)
• Turlough O'Carolan, blind itinerant harpist, "The Last of the Bards" (d. 1738)
• Aogán Ó Rathaille, poet (d. 1728)
• Approximate date – Cornelius Ó Caoimh, Roman Catholic Bishop of Limerick (d. 1737)

• William FitzWilliam, 3rd Viscount FitzWilliam, noble (b. c.1610)
• Probable date – James Arthur, Dominican friar and theologian.