ABSTRACT: Nummulitoidea are larger benthic foraminifera, and were major reef-forming organisms from the Middle Paleogene to Early Neogene. Today, porous nummulitoid limestones, which occur globally from the Atlantic to the Indo-Pacific, form potentially valuable oil reservoirs. Until now the origin, evolution and palaeogeographic development of the nummulitoids have not been fully articulated, but new material allows here the first systematic, global biostratigraphic comparison and correlation of the nummulitoids to be made. It is suggested that the nummulitoids originated in the Americas during the Middle Paleocene (Selandian). These early nummulitoids are inferred to have migrated across theAtlantic in the Late Paleocene (Thanetian) following two paths: south towards SW Africa, and northeastward through the Tethyan corridor. The Tethyan forms evolved during the Eocene into many lineages,which in turn migrated, within a few million years of their first appearance, into the Indo-Pacific, where they became isolated and diversified further. Meanwhile the SW African forms remained small and similar to the original American stock until the Early Miocene (Burdigalian), when assemblages were augmented by forms that migrated from Tethys, an event tablished by the discovery of new Mediterranean-derived species of Planostegina in SW Africa: africana, mcmillania, southernia, langhiana. Climatic and tectonic processes contributed to the Middle Oligocene disappearance of Nummulites and the Early Miocene global extinction of Spiroclypeus and of Cycloclypeus in the Mediterranean. Morphologically small nummulitoids persisted however, and are still present in all provinces to this day.