This Cities that Work paper first outlines why secure, legally enforceable and marketable land rights play such a pivotal role in urban development. Section 2 discusses the trade-offs associated with different tenure systems, both formal and informal. Whilst there can be strong benefits in formalising land rights, processes of formalisation need to be underpinned by well-functioning institutions to ensure benefits can be felt. Section 3 therefore focuses on successful reforms from across developing countries aimed at strengthening land-related legal and administrative systems. Finally, where policymakers decide to undergo a formal process of land registration, section 4 addresses the key challenges policymakers face in the process of implementing such programmes. These include reducing the cost of mapping and surveying procedures, and effective mechanisms to resolve competing claims over land ownership.