There were only less than sixty records of freshwater red algae in Finland until the 1980s, when the author began sampling the running waters of southern and central Finland; 516 new records were made in 1984–2011. More intensive research began in 2012, with a few field teams working at first in Central Finland Province and then covering the whole country. The project continued until 2018. During these studies approximately 3400 new locations were investigated and 3641 new records of 29 taxa were made. Since 2013, 12 ecological variables have also been measured or estimated. The share of positive records from the studied locations varied from 49% to 86% (avg. 72%), being highest in Lapland (85.5%). The most frequent taxa were Batrachospermum gelatinosum (36.5%), Audouinella hermannii (14.5%), Sheathia arcuata (9.3%), Sirodotia suecica (8.4%), Audouinella chalybea (4.7%), Lemanea fluviatilis (3.8%) and Lemanea fucina (2.8%). Batrachospermum elegans, Kumanoa virgatodecaisneana and Lemanea mamillosa occurred in southwestern Finland in waters with higher conductivity, whereas Batrachospermum turfosum and Virescentia vogesiaca were typical taxa of acidic and soft water. Batrachospermum sporulans and Lemanea condensata occurred only in northern Finland. Some records did not fit the recent morphological keys and should be analysed using molecular methods.