| Thomas J. O'Brien | |
| State1: | Illinois |
| Term Start1: | January 3, 1943 |
| Term End1: | April 14, 1964 |
| Predecessor1: | A. F. Maciejewski |
| Successor1: | Daniel J. Ronan |
| Term Start2: | March 4, 1933 |
| Term End2: | January 3, 1939 |
| Predecessor2: | James T. Igoe |
| Successor2: | A. F. Maciejewski |
| Office3: | Cook County Sheriff |
| Term Start3: | 1938 |
| Term End3: | 1942 |
| Predecessor3: | John Toman |
| Successor3: | A. L. Brodie |
| Birth Date: | 30 April 1878 |
| Birth Place: | Chicago, Illinois |
| Death Place: | Bethesda, Maryland |
| Resting Place: | Queen of Heaven Cemetery |
| Party: | Democratic |
Thomas Joseph O'Brien (April 30, 1878 – April 14, 1964) of Chicago was a U.S. Representative from Illinois, 1933–39, 1943–64, and as Cook County Sheriff from 1938 through 1942.[1] He was of the Democratic Party.[2] He became the "Dean" of Chicago delegates and played a role in the early career of Dan Rostenkowski.[3]
O'Brien died in office of a stroke on April 14, 1964, and was buried at Queen of Heaven Cemetery in Hillside, Illinois.[4]
The T.J. O'Brien Lock and Dam approximately 7 miles from Lake Michigan on the Calumet River in Chicago at the head of the Illinois Waterway is named after Congressman O'Brien.