The share of migrants in the total population in OECD countries has gradually risen to 11% in 2022. However, not all places experience migration to the same extent. Migration is significantly shaped by geography, and migrant shares can vary significantly across cities and regions within countries. The lack of geographically detailed data has made it difficult to fully understand how migrants settle within countries. The new OECD Municipal Migration Database (MMD) aims to fill this gap by gathering and organising detailed data for 22 OECD countries from 1991 to 2022. In addition to collecting information at the municipal level, the database also harmonises this information according to OECD regional typologies and functional urban areas (FUAs), enabling cross-country comparisons of the presence of migrants in consistently defined regional units or local labour markets. Key findings from the data reveal a notable concentration of migrants in large metropolitan regions, where approximately six out of ten migrants reside, compared to only five out of ten native-borns. Moreover, settlement patterns differ between cities in and outside of Europe, as well as between migrants from the European Union (EU) and non-EU countries in Western Europe, showcasing distinct migration dynamics.