In the works of J. R. R. Tolkien, Ossė was a Maia associated with Ulmo. A spirit of the sea in the service of Ulmo, he guarded the waters around Middle-earth. Uinen was his wife, and he was a friend of Cķrdan the Shipwright.

Ossė was a friend of the Sindar, and was valued as high as the Valar by them.

In older versions of The Silmarillion, Ossė was a Vala in his own right, and often opposed the will of Ulmo.