| William W. Arnold | |
| Office: | Judge of the United States Tax Court |
| Term Start: | September 16, 1935 |
| Term End: | June 30, 1950 |
| Predecessor: | Jed C. Adams |
| Successor: | Stephen E. Rice |
| State1: | Illinois |
| Term Start1: | March 4, 1923 |
| Term End1: | September 16, 1935 |
| Predecessor1: | Edwin B. Brooks |
| Successor1: | Laurence F. Arnold |
| Birth Name: | William Wright Arnold |
| Birth Date: | 14 October 1877 |
| Birth Place: | Oblong, Illinois, U.S. |
| Death Place: | Robinson, Illinois, U.S. |
| Party: | Democratic |
William Wright Arnold (October 14, 1877 – November 23, 1957) was an American politician and jurist, serving as a U.S. representative from Illinois and a judge of the United States Tax Court.
Born in Oblong, Illinois, Arnold attended the country schools of his native county and Austin College, Effingham, Illinois. He graduated from the law department of the University of Illinois in 1901. He was admitted to the bar the same year and commenced the practice of law in Robinson, Illinois. He was continuously engaged in the practice of his chosen profession until elected to Congress.
Arnold was elected as a Democrat to the Sixty-eighth and to the six succeeding Congresses and served from March 4, 1923, until his resignation, effective September 16, 1935, having been appointed July 29, 1935, a member of the United States Board of Tax Appeals (which became the United States Tax Court during his service). He was reappointed in 1944 and served until his retirement June 30, 1950. He owned and operated two large farms. He served as director of the Second National Bank, Farmers and Producers Bank, and the First National Bank of Robinson.
He died in Robinson, Illinois on November 23, 1957. He was interred in New Cemetery.