Thomas J. O'Brien (Illinois politician)

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. He was of the Democratic Party. He became the "Dean" of Chicago delegates and played a role in the early career of Dan Rostenkowski.

O'Brien died in office of a stroke on April 14, 1964, and was buried at Queen of Heaven Cemetery in Hillside, Illinois.

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.