Lieutenant General Douglas McKenzie Chalmers, CB, DSO, OBE (born 26 February 1966) is a former British Army officer who served as Deputy Chief of the Defence Staff (Military Strategy & Operations) from 2018 to 2021.

[5] He became commanding officer of the 2nd Battalion, Princess of Wales's Royal Regiment in July 2007 and, in that role, was deployed to Helmand Province, Afghanistan.

[3] Chalmers was deployed on Operation Inherent Resolve in Iraq in September 2015,[7] and became Deputy Commanding General-Support, III Corps and Fort Hood in August 2016.

[8] He was promoted to lieutenant general and was appointed Deputy Chief of the Defence Staff (Military Strategy & Operations) on 18 June 2018.

[14] In February 2021, it was announced that Chalmers would succeed Fiona Reynolds as Master of Emmanuel College, Cambridge.