Gruff, terse boss/commander/ringleader who directs and wields James Bond's MI6 (a.k.a. Her Majesty's Secret Service). In the case of the original one in the Bond stories, it was an eponymous code name; his real name was Admiral Sir Miles Messervy. M indeed.

In the James Bond films, the part of M has been played by Bernard Lee, Robert Brown, and (presently) Dame Judi Dench.