The World Arachnida Catalog (WAC, online at https://wac.nmbe.ch) is introduced as an amalgamation of the highly successful World Spider Catalog (WSC), the Pseudoscorpions of the World Catalog, and the Smaller Arachnid Order Catalogs. The new catalogs present all available taxonomic information on eight arachnid orders (Amblypygi, Araneae, Pseudoscorpiones, Ricinulei, Palpigradi, Schizomida, Solifugae and Uropygi) in a single location and a standardized format, continuously updated by specialists, to members of the World Spider Catalog Association (WSCA). For the first time, the majority of taxonomic literature for Pseudoscorpiones and the smaller arachnid orders will be available in downloadable PDF format for members according to the Swiss copyright laws. Up-to-date counts of families, genera and species are given alongside the current taxonomy for each taxon. Now in a common place and presented in an almost unified format, the new catalog aims to become the primary repository of taxonomic information for the Arachnida and will hopefully stimulate arachnological research across all arachnid orders by removing boundaries imposed by literature accessibility, incompatibility of formats, or taxonomic jargon.