James Butler Brennan (February 1, 1926 – June 6, 2021) was an American attorney and Democratic politician from the U.S. state of Wisconsin.

He served two years but resigned in April 1961 in anticipation of his confirmation as United States Attorney.

[2] In March 1961, newly elected president John F. Kennedy nominated Brennan to serve as United States Attorney for the Eastern District of Wisconsin.

[4] He was defeated in the 1984 election by his subordinate, Grant Langley, despite strong backing from the then-Mayor Henry Maier.

[5] After his defeat, he worked briefly as a staff attorney for the Milwaukee Metropolitan Sewerage District before resigning from that role in 1988.