This paper is a compilation and analysis of all vascular plants that have been reported on Kiritimati (Christmas) Atoll in the Northern Line Islands of the Republic of Kiribati. It is based on field inventories conducted by the authors on six field visits to the atoll between 1996 and 2012 plus available published and unpublished records of vascular plant collections and observations made on the atoll. The total number of vascular plant species that have been recorded at some time on Kiritimati, including all indigenous and introduced species (whether in cultivation or not) is 168, plus three hybrids and three additional varieties, making a total of 174 taxa. Of these, three records are doubtful, leaving a reliably reported total of 171 taxa in 166 species. Only 10 of the reported taxa were not seen by one or other of us in the period 1996–2012, and of these at least six have probably died out on the island, leaving an extant flora of around 165 reliably recorded taxa (including the hybrids and varieties) in 160 species. There have been no ferns or gymnosperms recorded on the island. Probably only 15 (9%) or perhaps up to 19 of the reliably reported species are native, and most of the present-day flora is made up of deliberate or unintentional introductions made since the date of European discovery of the atoll. Of these, at least 54 and perhaps up to 59 species have naturalized.