We present a comprehensive vascular flora of the Acadia National Park region of Maine based on over 20 years of recent fieldwork and a compilation of historic records and vouchers. We documented 1135 taxa of vascular plants (1055 species, 448 genera in 110 families) in the Acadia National Park region: 1079 taxa from Mount Desert Island, 708 taxa from Isle au Haut, and 398 taxa from Schoodic Peninsula. Over 20% of the taxa in the catalogue are historic records and have not been documented in the study area since 1980. Forty-five taxa historically published as extant in the study area were misidentified and are therefore not included in the flora. Non-native taxa represent 25% of the regional flora, 24 of these are invasive. Fourteen taxa listed as endangered or threatened in Maine have been documented in the study area, 12 of which have been observed within the last 10 years.