William Sewall Gardner (October 1, 1827 – April 4, 1888) was a justice of the Massachusetts Supreme Judicial Court from 1885 to 1887.

Born in Hallowell, Maine,[1][2] Gardner graduated from Bowdoin College and read law in Lowell, Massachusetts, gaining admission to the bar in 1852.

[2] He practiced law in partnership with Theodore H. Sweetser until 1875, when Gardner was appointed to the Massachusetts Superior Court, where he remained for ten years.

[2] In October 1885, Governor George D. Robinson appointed Gardner to a seat on the state supreme court vacated by the death of Justice Waldo Colburn.

In March 1887, he attempted to carry out his judicial duties in hearing cases from the bench, but due to poor health was only able to attend court for one day before taking leave, intending to travel to Europe to recover.