Sir Justinian Isham IV (8 July 1740 – 1 April 1818) was the 7th Baronet of Lamport and served in 1776 as High Sheriff of Northamptonshire.

Justinian Isham IV was born probably at Oxford, to Euseby Isham, the Vice-Chancellor of Oxford University and his wife Elizabeth (Mary) Panting.

He was educated at John Roysse's Free School in Abingdon, (now Abingdon School) and later was honorary Master of Arts and Bachelor of Laws at Lincoln College, Oxford.

On 18 February 1793, he was appointed a deputy lieutenant of Northamptonshire,[2] and died at the age of 77 years.

A painting of him by an unknown artist hangs at Lamport Hall.