William P. James (January 10, 1870 – July 28, 1940) was a United States federal judge.
Born in Buffalo, New York, James began his career in private practice in Los Angeles, California. He was a judge on the Superior Court of Los Angeles County, California from 1905 to 1910, and on the California Court of Appeals from 1910 to 1923.
On March 2, 1923, James was nominated by President Warren G. Harding to a new seat on the United States District Court for the Southern District of California created by 42 Stat. 837. He was confirmed by the United States Senate on March 3, 1923, and received his commission the same day. James served in that capacity until his death, in 1940.