Sir John Mitting (born 1947) is the current Chair of the Undercover Policing Inquiry (UCPI). In July 2017, he replaced the previous Chair, Sir Christopher Pitchford, who had to step down for health reasons As a result, the UCPI is sometimes referred to as the Mitting Inquiry.

He was a High Court judge sitting in the Queen’s Bench Division from 2001 until he retired in 2017. From 2007 to 2012, he was Chair of the Special Immigration Appeals Commission particularly dealing with appeals where national security issues were cited as a reason for excluding, deporting or detaining foreign nationals.
A leading criticism of him by non-state core participants (NSCPs) has been his uncritical trust in police accounts when former undercovers have sought anonymity. This contributed to the walk-out of NSCPs and their legal representatives in March 2018 in protest, calling on him to step down.
A contributing factor was that he had commented that married officers were less likely to have had sexual relationships with those they targeted. The events around this was set out in the NSCPs’ submissions of 19 March 2018:
7. In response to Ms Kaufmann’s submission that it is impossible to rule out wrongdoing on the basis of an individual’s personal or family circumstances, the Chairman explained his reasoning as follows:
“Of course it is impossible to rule it out, but you can make a judgment about whether or not it is more or less likely. We have had examples of undercover male officers who have gone through more than one long-term permanent relationship, sometimes simultaneously. There are also officers who have reached a ripe old age who are still married to the same woman that they were married to as a very young man. The experience of life tells one that the latter person is less likely to have engaged in extra marital affairs than the former.”
8. In response to further challenge on this issue from Ms Steel, the Chairman accepted being “somewhat naïve and a little old-fashioned” and undertook to revisit his views.
The NSCPs complained that Mitting’s views had persisted and were still influencing his approach when considering the anonymity of former undercovers. See also Criticism (sexism).
Mitting's membership of the Garrick Club, which until 2024 excluded women, was raised in a 2017 letter from women targeted for a relationships.