Finnlakeviridae is a family of bacteriophages that is the sole representative of its own class, Ainoaviricetes. 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.