Josiah Willis Crosby (November 24, 1816 – May 5, 1904) was an American lawyer and politician from Maine.

Despite illness, he studied law and was admitted to the Piscataquis County, Maine bar in 1838.

In 1845, he moved to Dexter, Maine, where he resided for the remainder of his life.

Politically, Crosby was first a Whig, then Republican, and finally a Democrat.

A graduate of Bowdoin College, he was actively involved in his alma mater's alumni association.