John Hart (died 1586) was an English Jesuit, known for his equivocal behaviour on the English mission in the early 1580s.
The son of William Hart of Eynsham, a recusant, he was abroad with his younger brother William. He was admitted to the English College, Rome where he took Roman Catholic minor orders in 1575. He took the degree of B.D. in the university of Douay in 1578, and was ordained priest on 29 March 1578 in Cambrai.
In June 1580 Hart was ordered to the English mission.
Arrested as soon as he landed at Dover, Hart was sent in custody to Nonsuch Palace and examined by Francis Walsingham. He was not immediately confined, but was instead given permission to go to Oxford to confer with theologians. He was subsequently placed in the Marshalsea Prison, and taken to the Tower of London on 24 December 1580.
On 15 November 1581, the day after Edmund Campion's condemnation, Hart was tried with other priests and condemned to death. On 1 December 1581 he was to have been executed with Campion, Ralph Sherwin, and Alexander Briant, but when placed on the hurdle he promised to recant, and he was taken back to prison.
Hart then wrote to Walsingham what was an act of apostasy, a document that has survived. He later retracted it. What Hart agreed with Walsingham at this point is that he would inform on William Allen, using a claim to having been racked to add to his credibility. Hart then retracted the offer, was condemned to die on 28 May 1582, and then was reprieved again. It is stated that on 18 March 1582, while in prison, Hart was admitted into the Society of Jesus.