While increasing number of proteins are suggested to be involved in regulation of R-loops or RNA:DNA hybrids, a complete understanding of regulatory network underlying R-loop homeostasis remains elusive. We are presenting our efforts here towards filling in this gap. To collect known proteins involved in R-loop regulation from scattered literatures, we downloaded all PubMed publications using "R-loop" OR "R-loops" OR "RNA DNA hybrid" OR "RNA DNA hybrids" OR "DNA RNA hybrid" OR "DNA RNA hybrids" as query for manual curation of R-loop regulators. For four species including human, mouse, yeast (Saccharomyces cerevisiae) or E. coli, a protein is considered as an R-loop regulator if it binds to, stabilizes, resolves or degrades RNA:DNA hybrids, or levels of R-loops or RNA:DNA hybrids are changed upon chemical or genetic manipulation of the protein. Provided on the Regulator page are basic information, supported evidences, molecular functions and key references. In total, 1,185 proteins in human, 24 in mouse, 63 in yeast (Saccharomyces cerevisiae) and 21 in E. coli were collected as R-loop regulatory proteins in current version (03-31-2021).