The next full moon isn't slated to occur until March 14 ... but John Fury couldn't wait a few days -- flashing his bare rear to the cameras while out for a stroll across the pond on Monday!!
John, Tyson, Tommy and Shane Fury were spotted leaving a café in the UK ... with the 59-year-old deciding the best pose for the cameras was to drop trou'.
The former world heavyweight champion didn't seem to be amused by his father's actions -- opting to keep it casual with the cameras.