Human-mediated activities such as trade, agriculture, and infrastructure development have contributed to the widespread introduction and establishment of alien plant species across various habitats in the Kingdom of Saudi Arabia (KSA). To achieve Target 6 of the Kunming-Montreal Global Biodiversity Framework, the geographical information gaps in invasion assessments must be addressed. Research on alien flora inventories from arid and semiarid regions is urgently needed, as they are under-represented in global alien species databases. Here, we provide an integrated and taxonomically verified checklist of alien flora found in KSA. Through field surveys and data from global databases, we compiled a standardized checklist of alien plant species in KSA. Species were categorized based on life span, growth form, and introduction pathways. A total of 215 alien species were documented, comprising 146 casuals, 28 naturalized species, and 41 invasive species. Among the life forms, therophytes dominate over phanerophytes and chamaephytes. North America, with 72 species, is the major source region of alien species. Out of the total species analyzed, nearly half were introduced unintentionally, making this the most common pathway. Roadsides and farmland habitats support the highest numbers of alien plant species, indicating their significant role as a conduit for the dispersal and establishment of alien species. Most invasive taxa occur in the central part of the country, with the highest number observed in the Makkah region. According to phylogenetic dissimilarity, regions in the central part of the country form a distinct group with a markedly higher number of invasive plants. These results may be related to environmental characteristics-the country's northern and southern areas are mostly arid desert, while the central-western area is more mountainous. Our study provides standardized, up-to-date information on the origins and introduction statuses of alien plant species in KSA, which represents a foundation for organizing and guiding initiatives aimed at stopping or at least mitigating the threats posed by invasive alien plant species.