William Henry Barnes (May 14, 1843 – November 10, 1904) was an American jurist who served as Assistant Justice on the Arizona Territorial Supreme Court from 1885 till 1889.

[4] After leaving school he established a legal practice in Jacksonville, Illinois, where he specialized in corporate law.

[4] After President Grover Cleveland was inaugurated, Adlai Stevenson I, Lyman Trumbull, and other members of the Illinois congressional delegation recommended Barnes for a territorial judgeship.

[10][11] The new Associate Justice was assigned to Arizona Territory's first district, comprising Cochise, Graham, and Pima counties.

In Johnson v. Tully (1887), 2 Arizona 223, he ruled that because the plaintiff had agreed to a settlement of $4,304.93 in a suit before the Arizona Territorial Supreme Court, he had given up the option of further appeal to the Supreme Court of the United States which required a minimum contested sum of $5,000 in any appealed dispute.

The dispute resulted in a telegram being sent by the jury foreman to the Attorney General claiming that Barnes was exerting inappropriate influence upon government witnesses.

[15] Upon learning of the telegram, Judge Barnes dismissed the Grand Jury, calling them "a band of character assassins, unworthy to sit in any court of justice.

The Department of Justice instead cited the fact that Barnes had accepted $900/year in pay from the territorial treasury on top of the $3000/year salary offered by the Federal government.

[17] On October 17, 1889, a couple weeks after the telegram was sent, President Benjamin Harrison nominated Richard Elihu Sloan as Barnes' replacement.

[22] Barnes died in his home around 9:00 pm on November 10, 1904, after becoming suddenly ill.[3][4] He was buried in Tucson's Evergreen Cemetery.