We summarize 121 14C and in-situ cosmogenic (10Be and 36Cl) ages that constrain fluctuations of the Irish Ice Sheet (IIS) since the Last Glacial Maximum (LGM) that can be linked to abrupt climate changes in the North Atlantic region. These data provide a robust means to date ice-sheet fluctuations because similar-age events can be identified from widely spaced sites, they are constrained by stratigraphy, and they can be related to large changes in the configuration of a dynamic ice sheet. The following events are recognized. (1) AMS 14C ages and 10Be and 36Cl ages as well as offshore data suggest that the last maximum advance of the IIS occurred between ∼27 and 23 cal ka. (2) Deglaciation began on the western continental shelf and in the Irish Sea Basin at ∼23 cal ka. Dated sites from around Ireland constrain subsequent widespread retreat of ice-sheet margins from the shelf onto Irish coastlines during the Cooley Point Interstadial ≥20 cal ka. AMS 14C ages suggest that the Cooley Point Interstadial continued until ≤18.2 cal ka B.P. During this interstadial, retreat of the ice-sheet margin into the northern Irish Sea Basin indicates that the IIS may have lost up to two-thirds of its mass. (3) Dated sites from northwestern and eastern Ireland indicate that the Cooley Point Interstadial was terminated by ice readvance during the Clogher Head Stadial at ∼18.2 cal ka. (4) The Linns Interstadial was a brief interval (≥17.0–≥16.5 cal ka) of ice recession following the Clogher Head Stadial that is identified from raised marine sediments in eastern and northern Ireland and cosmogenic ages elsewhere in Ireland. (5) The IIS subsequently readvanced during the Killard Point Stadial, reaching its maximum extent ∼16.5 cal ka, indicating that the readvance began sometime earlier. (6) Widespread retreat of the IIS began by ∼15.5 cal ka during the Rough Island Interstadial. (6) Readvance of cirque glaciers in western Ireland occurred during the Younger-Dryas equivalent Nahanagan Stadial.