John Pettit (June 24, 1807 - January 17, 1877) was a United States Representative and Senator from Indiana. Born in Sackets Harbor, New York, he completed preparatory studies and admitted to the bar in 1831. He moved to LaFayette, Indiana where he commenced practice in 1838; he was a member of the Indiana House of Representatives in 1838-1839 and was United States district attorney from 1839 to 1843.
Pettit was elected as a Democrat to the Twenty-eighth, Twenty-ninth, and Thirtieth Congresses (March 4, 1843-March 3, 1849); he was an unsuccessful candidate for renomination in 1848. In 1850 he was a delegate to the constitutional convention and a presidential elector on the Democratic ticket in 1852. He was elected to the U.S. Senate to fill the vacancy caused by the death of James Whitcomb and served from January 18, 1853, to March 3, 1855; he was an unsuccessful candidate for reelection in 1854. While in the Senate he was chairman of the Committee on Private Land Claims (Thirty-third Congress).
After his time in Congress, Pettit was chief justice of the United States courts in the Territory of Kansas from 1859 to 1861, and was a judge of the Indiana Supreme Court from 1870 to 1877. He died in LaFayette; interment was in Greenbush Cemetery.