This joint project has three streams of work: a macro-level approach to tracking and measuring subnational public climate finance flows using aggregate, internationally comparable data; a complementary revenue tracking stream that features a compendium of qualitative data on specific climate-related public revenue sources available to subnational governments in OECD and EU countries to support their climate action; and finally, a micro-level approach focused on subnational green budgeting. This dataset is part of the macro-level analysis to track and measure subnational government climate expenditure and investment in OECD and EU countries. It displays internationally comparable data on climate-significant expenditure and investment over the period 2001-2019. It covers a total of 33 countries for climate-significant expenditure and 32 countries for climate-significant investment, both federal and unitary countries, of which 30 are OECD member countries and 25 are EU member states.   The dataset encompasses several sectors of government: General Government (S13 – non-consolidated), State Government (in federal countries), Local Government (in all countries), and Subnational Government. The Subnational Government sector is equivalent to the sum of the State and Local Government sectors in federal countries, and to the Local Government sector in unitary countries. In unitary countries, the Local Government Sector includes regional, intermediary and local governments, depending on countries’ institutional organisation at the subnational level. The estimates for climate-significant expenditure and investment are expressed through different measures, including USD PPP, USD PPP per capita, and ratios in GDP and General Government. PPPs conversion rates equalise the purchasing power of different countries and thus allow for comparison among OECD and EU countries. Converting the data in USD PPP also facilitates the computation of weighted averages for groups of countries – such as OECD, EU or OECD federal countries.  This dataset uses the Classification of the Functions of Government (COFOG) statistical classification system, from the OECD National Accounts, Eurostat and IMF Government Finance Statistics datasets. To categorise expenditure and investment that are "climate-significant", a methodology was developed, based on the EU Taxonomy on Sustainable Activities. Based on this methodology, three first-level COFOG functions (Economic Affairs, Environmental Protection, and Housing and Community Amenities) and 12 second-level COFOG functions were identified as “climate-significant” (namely COFOG 04.2: Agriculture, forestry, fishing and hunting; 04.3: Fuel and energy; 04.5: Transport; 05.1: Waste management; 05.2: Wastewater management; 05.3: Pollution abatement; 05.4: Protection of biodiversity and landscape; 05.5: R&D Environmental Protection ; 05.6: Environment n.e.c ; 06.1: Housing development; 06.2: Community Development; 06.3: Water supply; 06.4: Street lighting). In order to identify the share of expenditure in each second-level COFOG function that could be considered climate-significant, proxy coefficients and policy lenses, derived from internationally comparable datasets, were applied to each function. The dataset is accompanied by a Technical Report (Subnational Government Climate Finance Tracking: Technical Report-LINK) which includes a detailed explanation of the methodology used to develop the database. The scope and time coverage of data differs across countries based on availability. The following OECD and EU countries are not included in the database due to a lack of data: Canada, Chile, Colombia, Costa Rica, Cyprus, Korea, Malta, Mexico, New Zealand and the United States.