Sea lemon is a loosely applied common name for a group of medium-sized to large shell-less colorful sea slugs or nudibranchs, specifically dorid nudibranchs in the taxonomic family Dorididae and other closely related families. These are marine gastropod mollusks.

The Monterey sea lemon is Doris montereyensis and the mottled pale sea lemon is Diaulula lentiginosa.

The common name sea lemon probably comes from these animal's visual similarity to a lemon based on such qualities as the roughened skin, the oval form when seen from above, and the common but not inevitable orange to pale yellow coloration.

Dorididae. Retrieved May, 08 2021, from en.wikipedia.org/wiki/Dorididae.