George Griswold Sill (October 26, 1829 – May 19, 1907) was an American politician who was the 57th Lieutenant Governor of Connecticut from 1873 to 1877.

After preparatory studies at Ellington Academy, he attended Yale University from 1848 to 1852 and was a member of Skull and Bones.

When the American Civil War broke out, he organized the first company of Connecticut Volunteers in his office and went to the front.

In 1873, he was nominated by the Democrats for the election for Lieutenant Governor of Connecticut and won a large plurality.

He served in four consecutive one-year terms, while Charles R. Ingersoll was the Governor, from May 7, 1873, to January 3, 1877.