<P> A total of 113 people have served on the Supreme Court of the United States, the highest judicial body in the United States, since it was established in 1789 . Supreme Court justices have life tenure, and so they serve until they die, resign or retire, or are impeached and removed from office . For the 105 non-incumbent justices, the average length of service was 6,203 days (16 years, 359 days). Their length of service ranges from William O. Douglas's 13,358 days (7004133580000000000 ♠ 36 years, 209 days) on the Court to the 163 - day tenure of Thomas Johnson . Among the current members of the Court, Associate Justice Clarence Thomas is the longest - serving justice, with a tenure of 7003980700000000000 ♠ 9,807 days (7003980700000000000 ♠ 26 years, 310 days) as of August 29, 2018 . </P> <P> The table below ranks all United States Supreme Court Justices by time in office . For five individuals confirmed for associate justice, and later confirmed for chief justice separately--Charles Evans Hughes, William Rehnquist, John Rutledge, Harlan F. Stone, and Edward Douglass White--their cumulative length of service on the Court is measured . The basis of the ranking is the difference between dates; if counted by number of calendar days all the figures would be one greater, with the exception of Charles Evans Hughes and John Rutledge, who would receive two days, as each served on the Court twice (their service as associate justice and as chief justice was separated by a period of years off the Court). The start date given for each justice is the day he or she took the prescribed oath of office, with the end date being the date of the justice's death, resignation, or retirement . A highlighted row indicates a justice currently serving on the Court . </P>

Who is the longest sitting supreme court justice