Thomas Allen Jenckes (November 2, 1818 – November 4, 1875) was a United States Congressional representative for the State of Rhode Island. Jenckes was best known for introducing a bill that created the United States Department of Justice. President Ulysses S. Grant then signed the bill into law on June 22, 1870. Jenckes was also an avid supporter of civil service reform.Jenckes graduated from Brown University in 1838. Jenckes was admitted to the Rhode Island state bar in 1840.