A marine planktonic ciliate, belonging to the genus Askenasia Blochmann, 1895, is described with notes on its distribution and ecology. Specimens of this new species were collected from four coastal sites across the northern hemisphere. Samples were collected between March and December, from depths of 1–20 m. Relatively low (< 1 ml⁻¹) densities were recorded from Atlantic and Pacific Oceans and North Sea coastal sites, whereas samples from the English Channel suggested that this species has the ability to form blooms. Specimens were protargol-stained, revealing the key features of the genus, including the diagnostic sub-equatorial kinety belt consisting of three unciliated monokinetids. However, the species is larger than other Askenasia with a single distinctive, rope-like, scalloped macronucleus. This species also appears to have an extra somatic kinety belt, which may be present but has not been observed in other Askenasia species. Based on size, kinety structure, kinety number, and macronuclear shape a new species has been established.