William George Crosby (September 10, 1805 – March 21, 1881) was an American politician and the 23rd Governor of Maine.

He then studied law with his father, Judge William Crosby, was admitted to the bar, and practiced in Boston.

Crosby served as delegate to the 1844 Whig National Convention that nominated Henry Clay for President of the United States.

From 1846 to 1849, Crosby served as secretary of the Maine Board of Education, the first person to hold this position.

After leaving the office, he served as a trustee of Bowdoin College and a member of the Maine Historical Society.