Ulva is a genus of green algae known commonly as sea lettuce or green laver. Ulva seaweeds are found worldwide in nitrogen-rich marine habitats attached to rocks in the mid to low intertidal zone (Lee 2008; Kirby 2001). The fronds of Ulva usually grow as sheets, but some species exist in a hollow cylindrical form. These cylindrical species were previously classified as a distinct genus, Enteromorpha, but are now included in Ulva. (Lee 2008; Hayden et al 2003). The blades can grow up to 40 cm long, but are very thin—only 2 cells thick (Lee 2008).

Ulva is eaten by humans in soups, salads, and sushi (Lee 2008 and references within; Kirby 2001).