Manufacturer Mars is to bring back the original name in a three-month trial.
It is the latest in a line of relaunches for retro brand names, coming just weeks after the same company announced plans to bring back another former British favourite, Opal Fruits.
Marathon was renamed Snickers in 1990, after Mars decided to scrap the British brand and bring it into line with its global operation. For a period the wrapper of the bar carried both names, before Marathon was removed. The move made the bar something of a cultural reference point.
But the name has now been re-registered as a UK trademark.
Snickers is the best-selling chocolate bar of all time and has annual global sales of £1 billion. It was first created by Mars in 1930 and is believed to have been named in memory of a horse belonging to the owners.