Alastair Mars
Lieutenant Alastair Mars during his time as captain of HMS Unbroken  | |
| Born | 1 January 1915 St John's, Dominion of Newfoundland  | 
| Died | 12 March 1985 Ipswich, Suffolk, England  | 
| Allegiance | United Kingdom | 
| Branch | Royal Navy | 
| Years of service | 1932–1952 | 
| Rank | Lieutenant Commander | 
| Commands | HMS Unbroken HMS Thule  | 
| Battles / wars | World War II
  | 
| Awards | DSO DSC and bar | 
| Other work | Author of several autobiographies and novels. | 
Lieutenant Commander Alastair Campbell Gillespie Mars, DSO, DSC and Bar (1 January 1915 – 12 March 1985) was a Royal Navy World War II submarine commander.
In 1952, he was court martialled and dismissed from the service under controversial circumstances and pursued a career as an author.