William Arthur Sloane (October 10, 1854 – April 21, 1930) was an associate justice of the Supreme Court of California from May 15, 1920, to January 1923.

In 1912, Sloane was a Republican Party delegate to the national convention in Chicago, Illinois, pledged to support Theodore Roosevelt for President of the United States.

Sloane was re-elected to that office, which he held until January 1, 1919, when Governor William Stephens appointed him to the newly created Second Division of the California Court of Appeal, Second District.

[7] In November 1922, Sloane ran unsuccessfully for re-election, campaigning on the point he was the sole candidate from Southern California.

[11] Precinct returns show Sloane carried the Los Angeles vote, but lost the race in the San Francisco ballots.