The European Commission is a crucial actor in EU climate policy in three regards. First, based on its unique role in the EU system as an initiator of policy proposals, it acts as a policy entrepreneur, contributing to the gradual advancement of EU climate policy (Dupont et al. 2020(Dupont et al. : 1104Laffan 1997; Skjaerseth and Wettestad 2010). In this role, it has promoted commitments to ever more ambitious greenhouse gas (GHG) emission reduction targets (compared to 1990 levels) that, once agreed, served as the basis for the Commission's legislative initiatives. Second, as guardian of the treaties (Treaty on the EU (TEU) Art. 17), the Commission monitors EU countries' compliance with the adopted legislation. To this end, it has constantly improved coordination processes with national governments (Börzel and Buzogany 2019, Bürgin 2021, Peeters and Athanasiadou 2020, Schoenefeld and Jordan 2020). Finally, the Commission is actively involved in EU international climate policy, coordinating bi-lateral and multilateral partnerships on climate change and energy with third countries, contributing to knowledge transfer and policy learning (Biedenkopf and Torney 2014).The Commission's motivation to push for an ambitious climate policy is twofold. Firstly, it naturally serves the Commission's institutional self-interest to strengthen its role within the governance of the EU. Secondly, and more importantly, the Commission has an obligation to fulfil its responsibilities, as set out in the treaties. In line with this duty, the Commission considers an ambitious climate policy in response to public demand as a powerful engine for European integration, in particular in a context of shrinking citizens' trust in the EU and its institutions, and also as a means to strengthen the EU's role on the global stage (European Commission 2020d, Skovgaard 2013: 1147.The remainder of this chapter is structured as follows. The first section outlines the Commission's political and administrative structure and provides an overview of the interservice coordination in the policymaking process. The second section describes the main competences of the Commission, which include initiating proposals, monitoring and enforcing implementation, and representing the EU in international cooperation. The final section is an assessment of the constraining and enabling factors for the Commission's climate policy entrepreneurship, such as international context conditions, the position constellation among the two co-legislators, as well as the Commission president's internal leadership capacity and strategies.