Pinna is a genus of bivalve molluscs belonging to the family Pinnidae.

[2] The most extensively studied species in the genus is P. nobilis, a Mediterranean pen shell which was historically important as the principal source of sea silk.

They are characterized by thin, elongated, wedge-shaped, and almost triangular shells with long, toothless edges.

Pinna is distinguished from its sibling genus Atrina by the presence of a sulcus dividing the nacreous region of the valves, and the positioning of the adductor scar on the dorsal side of shells.

These bivalves most commonly lie point-first on the sea bottom in which they live, anchored by a net of byssus threads.