| John P. Barnes | |
| Office: | Senior Judge of the United States District Court for the Northern District of Illinois |
| Term Start: | September 15, 1957 |
| Term End: | December 31, 1958 |
| Office1: | Chief Judge of the United States District Court for the Northern District of Illinois |
| Term Start1: | 1948 |
| Term End1: | 1957 |
| Predecessor1: | Office established |
| Successor1: | Philip Leo Sullivan |
| Office2: | Judge of the United States District Court for the Northern District of Illinois |
| Term Start2: | March 4, 1931 |
| Term End2: | September 15, 1957 |
| Appointer2: | Herbert Hoover |
| Predecessor2: | Seat established by 46 Stat. 1417 |
| Successor2: | Julius Howard Miner |
| Birth Name: | John Peter Barnes |
| Birth Date: | 15 March 1881 |
| Birth Place: | Beaver County, Pennsylvania |
| Death Place: | Elgin, Illinois |
| Education: | Geneva College (B.S.) University of Michigan Law School (LL.B.) |
John Peter Barnes (March 15, 1881 – April 10, 1959) was a United States district judge of the United States District Court for the Northern District of Illinois.
Born in Beaver County, Pennsylvania, Barnes received a Bachelor of Science degree from Geneva College in 1904 and a Bachelor of Laws from the University of Michigan Law School in 1907. He was in private practice in Chicago, Illinois from 1907 to 1913. He was a first assistant county attorney of Cook County, Illinois from 1913 to 1914, thereafter returning to his private practice until 1931.
On February 26, 1931, Barnes was nominated by President Herbert Hoover to a new seat on the United States District Court for the Northern District of Illinois created by 46 Stat. 1417. He was confirmed by the United States Senate on March 2, 1931, and received his commission on March 4, 1931. He served as Chief Judge from 1948 to 1957, assuming senior status on September 15, 1957, and resigning the bench altogether on December 31, 1958.
Barnes was also a basset hound breeder, and was co-owner of Barook Kennels from 1957 until his death on April 10, 1959, in Elgin, Illinois.