Type genome is Fontibacterium boreale Umea-bin-09620 (GCA_903909545.1), a metagenome-assembled genome (MAG) assembled from 1-5 m depth from Lake Bjarntjarnan, Sweden (date: 2018-01-01/07). Umea-bin-09620 has a genome size of 1 Mbp with a genomic GC content of 30.2% and contains 20 tRNAs. The genome is of high quality, consisting of 243 contigs, with a completeness of 96.4%, contamination of 0.1% and strain heterogeneity of 0% as assessed with checkM. The metagenome was assembled with Megahit (version 1.1.13) from short-read sequencing (Illumina MiSeq). Metagenomic fragment recruitment of >600 samples from five continents indicate that the species is present mainly in boreal lakes in Europe and North America. The closest cultivated relatives are Fontibacterium commune, syn. ‘Candidatus Fonsibacter ubiquis’ LSUCC0530 (GCF_002688585.1; later reclassified to ‘Ca. Allofontibacter communis’), with an average amino acid identity of 82.49% and average nucleotide identity of 81.54 % and another newly proposed species, Fontibacterium abundans MiE-29 (GCA_965235095.1), with an AAI of 84.48% and an ANI of 83.54 %. Current GTDB classification (R220): d__Bacteria; p__Pseudomonadota; c__Alphaproteobacteria; o__Pelagibacterales; f__Pelagibacteraceae; g__Fonsibacter; s__.