This report presents an Integrated Marginal Abatement Cost Curve (iMACC) for Ireland’s energy system, quantifying the emissions reduction potential and marginal abatement costs of key mitigation measures across electricity generation, transport, buildings, industry and bioenergy over the period 2026–2050. Two iMACCs are presented, assessing the scale, cost and structure of mitigation under a modelled version of current policies scenario, based on With Additional Measures (WAM) - and a more ambitious 300 MtCO₂eq carbon budget pathway. Together, these analyses provide insight into the technologies and sectors that contribute most significantly to emissions reduction and the additional effort required to achieve deeper decarbonisation.