Finnlakeviridae is a family of bacterial viruses that is the sole representative of its own class, Ainoaviricetes (from "ainoa", the Finnish word for "single" + -viricetes). The family contains a single genus, Finnlakevirus, which contains a single species, Finnlakevirus FLiP. This virus was isolated in 2010, with its gram-negative host Flavobacterium, from Lake Jyväsjärvi, a boreal freshwater habitat in Central Finland, and is the first described single-stranded DNA virus with an internal membrane.

The genome is circular single-stranded DNA of about 9200 nucleotides in length.