Kyllinga mbitheana, a new species, is described from eastern Kenya and its conservation status assessed. The species is a tufted perennial to 200 mm tall, with white inflorescences and glumes to 2.5 mm long. Kyllinga mbitheana is most similar to K. microbulbosa and K. brunneoalba, but is unique in Kyllinga, being the only species with a spikelet bearing up to ten fertile flowers. The spikelet has an indeterminate rachilla with distichously arranged glumes, and the floral ontogenetic pattern is similar to that of other Cyperoideae. The diagnostic laterally compressed nutlets can be observed in the ontogenetic phase, where the dorsiventrally orientated stigma primordia give rise to a laterally flattened ovary. The pollen grains have one distal pore and five lateral colpi, have micro-echinate sexine, and tapetum is covered by orbicules. This taxon is potentially insect pollinated.