Introduced (non-native) species that become established may eventually become invasive, so tracking introduced species provides a baseline for effective modeling of species trends and interactions, geospatially and temporally. The United States Register of Introduced and Invasive Species (US-RIIS, https://doi.org/10.5066/P95XL09Q), as of 2021-11-08, is comprised of three lists, for the localities of Alaska (AK, with 532 records), Hawaii (HI, with 6,075 records), and the conterminous United States (L48, with 8,657 records). Each includes introduced (non-native), established (reproducing) taxa that: are, or may become, invasive (harmful) in the locality; are not known to be harmful there; and/or have been used for biological control in the locality. To be included in the US-RIIS, a taxon must be non-native everywhere in the locality and established (reproducing) anywhere in the locality. Native pest species are not included. Each record has information on taxonomy, dates of introduction (where available; currently for 38% of the records), invasion status (invasive or introduced), and citations for the authoritative sources from which this information is drawn. The US-RIIS builds on a previous dataset, A Comprehensive List of Non-Native Species Established in Three Major Regions of the U.S.: Version 3.0 (Simpson et al., 2020, https://doi.org/10.5066/p9e5k160). There are 15,264 records in the master list and 12,981 unique names. The list is derived from 5,951 authoritative sources, was reviewed by or based on input from 30 invasive species scientists, and continues to be updated. Publication of version 2.0 of the US-RIIS is anticipated (but not guaranteed) in approximately 12 months.