Thuridilla lineolata is a species of sea slug, a sacoglossan, a marine gastropod mollusk in the family Plakobranchidae.

It is an Indo-Pacific species that lives in or near coral reefs and eats algae.

This species occurs in the tropical West-Pacific, mainly in Indonesia and the Philippines.

The mantle is bright blue, and the edges of the parapodia are framed by two lines: a fine black one and an orange one on the external side.

The smooth rhinophores and the oral cavity are also marked with a black line and with an orange band.