The objective of this study is to provide a detailed taxonomic resource for identifying and studying ants in the genus Pheidole that have established beyond their native ranges. There is an increasing need for systematists to study taxa of specific concern to 21^st century environmental, food security and public health challenges. Systematics has an important role to play in both the theoretical and applied disciplines of invasion biology. Few invaders impact terrestrial ecosystems more than ants. Among the world's 100 worst invasive species is the cosmopolitan and highly destructive Pheidole megacephala (Fabricius). Accurate identification of P. megacephala is imperative for the success of screening, management and eradication programs designed to protect native ecosystems from the impacts of this destructive species. However, accurate identification of Pheidole species is difficult because of their taxonomic diversity, dimorphic worker caste and lack of taxonomic resources. Illustrated keys are included, along with the taxonomic history, taxonomic diagnoses, biological notes and risk statements for the 14 most invasive members of the genus. Global distribution maps based on over 14,000 specimen and literature records are presented for each species. These results of this work will facilitate identification of pest species, determination of climatic and habitat requirements, discovery of pest origins, horizon scanning and assessment of invasion pathways. The following new synonym is proposed, with the senior synonym listed first and the junior synonyms in parentheses: Pheidole indica Mayr (= P. teneriffana Forel, and its synonyms P. taina Aguayo and P. voeltzkowii Forel). Pheidole navigans Forel, stat. rev., stat. n. is removed from synonymy and elevated to species rank. It is proposed that records of P. moerens Forel outside of the Mesoamerica and the Caribbean refer instead to P. navigans or other heterospecific taxa in the P. flavens species complex. We propose that the names P. anastasii Emery and P. floridana Emery have been widely misapplied to North American outdoor records of P. bilimeki Mayr. It is suggested that the synonymy of P. lauta Wheeler be transferred from P. floridana Emery to P. bilimeki Mayr.