The Irish local government sector is a key public sector body with respect to the State meeting its climate change ambitions of carbon neutrality by 2050. Its broad operational remit in providing over 1,000 services, many of which require climate-proofing, and its close relationship with communities, means that it is a key public sector body if national and EU climate commitments are to be met. In light of various policy and legislative requirements in recent years, the sector has committed to monitoring, evaluating and reporting annually on the implementation of activities contained in the Local Authority Climate Action Charter, a key policy agreed between central government and the sector in 2019. This research supports the sector through i) documenting the work that has taken place to date in the area of climate action, including policy developments nationally and internationally; ii) developing a comprehensive literature review to identify national and international best practice regarding the development of climate action Key Performance Indicators (KPIs); iii) comparing climate action KPIs across jurisdictions; and iv) exploring opportunities for the development of KPIs for the Irish local government sector aligned to KPIs in other jurisdictions. An extensive literature review integrating both academic publications and a selection of best practices across municipalities considered at the forefront of climate action globally was undertaken in March/April 2021. Results demonstrated a range of best practices in the development and implementation of climate action performance metrics, including ensuring indicators are clear, broad stakeholder support and engagement exists, climate action KPIs are mainstreamed, benchmarking policies and baseline periods are developed and indicators are simple to measure and report on. Whilst governance structures within the Irish local government sector are highly centralised in comparison to international standards, the literature typically identified KPIs as aligning to either mitigation or adaptation metrics. A total of 60 outcome KPIs that may offer some level of transferability or adaptability with respect to local authorities’ climate change ambitions were identified. This includes 36 mitigation metrics, 10 adaptation metrics and 14 metrics that are considered both mitigation and adaptation KPIs. These indicators relate to climate change mitigation and adaptation across 14 areas, including but not limited to energy, enterprise, environment, flood risk management, greenhouse gas emissions, housing, public engagement and transport. This research identified several findings that may be useful with respect to KPIs for the local government sector. First, capturing relevant metrics on process or policy indicators is an important first step in ensuring appropriate frameworks or policies are in place to begin with so that the sector can understand what initial supports or practices are necessary. Without such a framework, the outcome indicators identified herein may prove challenging to measure. Second, where performance metrics are initially developed, simplicity at the outset is essential. However, being equally ambitious in choosing metrics, and in capturing and improving climate action performance, is also important to ensure commitments and targets detailed in national climate change policy are fulfilled. And finally, whilst these indicators represent the most relevant metrics applicable to the sector, it is important to recognise the evolving nature of climate policy at both EU and national levels. Periodic reviews of indicators to ensure they remain relevant, are aligned with international best practice, and are applicable to current policy and local authority operations would therefore prove beneficial. The findings identified within this report may support the local government sector to deliver on its national climate action commitments and in demonstrating public sector climate action leadership.