Borealea nobilis is a species of sea slug, an aeolid nudibranch, a marine heterobranch mollusc in the family Flabellinidae.

[2] Borealea nobilis was described from a single specimen dredged in 145 m depth off Cape Cod in 1879.

It is widely distributed in the northern Atlantic Ocean from Norway south to Ireland and on the North American coast south to New England.

The digestive gland in the cerata is either orange or red in colour.

The rhinophores are pale yellow-brown in colour and covered with small papillae.