Diatoms are major primary producers known to respond rapidly to environmental change, making them useful indicators for ecological assessment and monitoring. In the Salish Sea bioregion, diatom records date back to early inventories by Lord (1866) and Bailey and MacKay (1916), followed by scattered surveys throughout the 20th and 21st centuries. Due to this fragmented record, a consolidated regional baseline has been lacking.We report 924 diatom taxa for the Salish Sea from historical records, voucher specimens and molecular data, forming a curated dataset of 11,469 records. Forty-two species, including six previously unreported genera, are newly recorded for the region, based on combined morphological and molecular evidence. For these taxa, including the recently described Andrzeja fenestrata, we provide taxonomic accounts with diagnostic light and electron micrographs. These data establish a baseline record of diatom diversity in the Salish Sea, setting an example for how collaboration amongst community and academic researchers can help establish data foundations for phytoplankton monitoring.