Air vice-marshal John "JE" Ernsting CB, OBE, FRCP, FRAeS (21 April 1928 – 2 June 2009) was a senior Royal Air Force (RAF) commander and renowned medical researcher.

Ernsting was born in Woolwich, London on 21 April 1928, and educated at Chislehurst and Sidcup Grammar School for Boys. From Guy's Hospital, he qualified in physiology in 1949 and in medicine in 1952.

In 1954, Ernsting was commissioned into the RAF Medical Branch, where he spent his entire military service.

While working in the Altitude Division of the RAF Institute of Aviation Medicine, he worked on Partial-pressure suit assemblies. He was head of this division for twenty years from 1957 to 1977. However, the RAF never issued a partial-pressure suit, preferring instead to use anti-g trousers in conjunction with pressure jerkins. He was the aeromedical project officer for the development of the United Kingdom's versions of the Phantom, F-111, and Hercules. He later became chairman of the aeromedical and life support system working parties for the Tornado and Typhoon.

In 1971 he became the RAF Consultant Adviser in Aviation Medicine, a position he held until 1990. Between 1990 and 1993 he served as Dean of Air Force Medicine, then as Senior Consultant (RAF).

Upon leaving the Altitude Division in 1977, he was first appointed Deputy Director of Research (1977–1985), then Director of Research (1985–1988), before becoming Commandant of the RAF Institute of Aviation Medicine (1986–1992). However, between 1979 and 1980, Ernsting spent a sabbatical year at the USAF School of Aerospace Medicine.

He was Queen Elizabeth II's honorary surgeon from 1989 to 1993.

He retired as commandant of the IAM in December 1992 and from the RAF on 21 April 1993.