Universally recognized scientific names for organisms are necessary for accurate and efficient communication. Incongruence in taxonomic treatments results in situations where one name is used for different entities or one entity is known by different names, with negative consequences for conservation, science, trade, legislation, law enforcement, and education, leading to discord among stakeholders and confusion among users. Within the ornithological community taxonomic incongruence among four widely adopted global bird checklists has led to calls for the development of a single unified global avian taxonomy or checklist. Here we introduce AviList, a comprehensive, collaborative and evolving effort towards developing a unified global avian taxonomy, spearheaded by representatives of most current global checklists and many major regional authorities, and supported by the International Ornithologists’ Union (IOU), BirdLife International and the Cornell Lab of Ornithology. AviList version 2025, the first version, was officially launched on 11 June 2025 and is available online as a comprehensive, searchable public-access database. It recognizes 11,131 bird species in 2376 genera, 252 families and 46 orders. This global effort has resolved over 1000 species-level taxonomic incongruences among existing checklists. With AviList’s launch, the IOC World Bird List and the Clements Checklist of Birds of the World have ceased any independent taxonomic updates, while BirdLife International is in the process of total alignment, leading to a harmonization in the classification underpinning a number of major bird projects, including eBird, Macaulay Library, Merlin Bird ID and the IUCN Red List. Adoption of AviList will improve inter-operability across global biodiversity, molecular, ecological and spatial databases (e.g. GBIF). Strong governance of AviList will ensure it is a “living” document that is regularly updated by a global community of bird taxonomists as new scientific advances are made, with positive impacts for conservation, academia and human society. It is hoped that AviList will support and encourage taxonomic science by identifying areas where further research is most needed, and that it will provide a blueprint for taxonomic authorities in other organismic groups endeavoring to achieve taxonomic harmonization.