The pair are making their comeback as part of a 30th anniversary special.
"It was an immediate yes when I was invited to return for the 30th anniversary, I wouldn't have missed it and I'm thrilled with the way their story unfolds," said Charleston.
There are no official details yet on the storyline surrounding their return.
"I spent half my working life on Neighbours and so it's lovely to be back with Anne and all the cast and crew," said Ian Smith, who plays Harold.
He retired from Neighbours in 2009.
Madge joined the series in 1986 as the mother of Charlene, played by Kylie Minogue. After her marriage failed, she married Harold Bishop.
Harold has already made one iconic return to the show, reappearing with amnesia, five years after being swept out to sea.
He renewed his vows with Madge after regaining his memory, before she died of pancreatic cancer a few years later.
The pair are currently filming their episode at the Neighbours studio in Melbourne.
Other cast members from previous years are thought to also be making a return as part of the celebration, although no official details have been confirmed.
Neighbours currently airs on Channel 5 in the UK and the anniversary special featuring Harold and Madge will be shown in 2015.
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Neighbours favourites Harold and Madge Bishop will be back on screens next year, despite the fact Madge, played by Anne Charleston, died in in 2001.