Before the 2017 election, Kenya’s President declared the minority ethnic Makonde community recognised as ‘the 43rd tribe of Kenya’. Unbeknown to them, in 2009 the National Bureau of Statistics had written to the Kenya Nubian Council of Elders to declare that they would be counted in the upcoming census as ‘the 43rd tribe’. But how are these decisions made? What does it mean to be recognised? What are the immediate consequences and the broader implications? This project provides a critical history of the census, internal boundaries, and special categories in law, and illustrative case studies of their contestation. It pays particular attention to the awkward tension between certainty, which is theoretically characteristic of categorisation, and uncertainty, which characterises the practices in real life. The project will shed new light on identity and politics in contemporary Kenya, as well as on enduring questions relevant across the region about ethnicity as a (post)colonial formation, the relevance of ideas of governmentality and legibility to ethnic politics, and the nature and role of (un)certainty. The project will also publicise practices of state categorisation of identity in Kenya that have so far remained opaque, and generate opportunity for public debate about these practices and their effects, including among statisticians, cartographers and law makers.