John Colvin[2][3] (or Colton)[4] Knox (February 18, 1817 – August 26, 1880) was a Pennsylvania lawyer and judge.

He served as a deputy attorney general 1840–1842, and was sent to the state legislature in 1845, which he left early when appointed president judge for various districts in western Pennsylvania.

[6] Knox's oldest son, Kilburn, had completed two years at the University of Pennsylvania when the Civil War broke out.

The night before the Lincoln assassination, Michael O'Laughlen (a childhood friend of John Wilkes Booth) showed up at the Stanton residence and made somewhat drunken inquiries that were handled by Kilburn.

Kilburn's testimony was the strongest link connecting O'Laughlen to the Booth conspiracy, and helped secure a conviction.