Hypselodoris festiva, the festive sea slug,[2] is a common species of colourful sea slug or dorid nudibranch, a marine gastropod mollusk in the family Chromodorididae.

This nudibranch was described from Tsushima, Korea Strait, Japan.

It is found in Japan, Hong Kong, and also Korea.

The rhinophores have blue shafts and red lamellae on the clubs.

The gill leaves are translucent white with a single red line on the outer edge and red lines on the inner edges.