The actress, who portrays Weatherfield's Michelle Connor, will make her debut as Elsie when Street of Dreams has its world premiere in Manchester on May 9.
As she explores Elsie's journey through the 1960s era, Marsh will also perform a rendition of 'I Know How It Feels' from the 2010 Coronation Street album Rogues, Angels, Heroes and Fools.
Pictured: Kym Marsh as Elsie Tanner.
Marsh commented: "The strong, determined and indomitable women have always defined Coronation Street right from the very first episode to the present day, and Elsie Tanner will go down in history as one of the most gossiped-about women in Weatherfield.
"She's left some rather big stiletto shoes to fill, but to have the opportunity to represent such an iconic character of yesteryear on a stage of this scale is an absolute honour."
Street of Dreams' composer Trisha Ward added: "I am thrilled Kym is joining the world premiere tour of Coronation Street: Street of Dreams to play Elsie Tanner. Elsie was at the very heart of Tony Warren's Coronation Street and a character that stayed with me through the process of writing a major musical around the world's most successful TV programme.
"Kym has a wonderful voice for Elsie's torch-song, 'I Know How It Feels', and embodies the same beauty and dynamic passion that embodied this most iconic of Tony's female characters."
West End star Jodie Prenger will also take to the stage alongside Marsh, playing the 1980s version of Elsie for the world premiere in Manchester.
Pictured: Jodie Prenger as Elsie Tanner.
Prenger said: "The entire production is just gorgeous, with infectious songs which stick in your head! The music is fabulous, the orchestration is phenomenal and the cast are truly amazing. To be asked to play such an amazing part in something that people will be telling their grandchildren about in years to come is just a dream."
As previously announced, Paul O'Grady will feature as the star of Street of Dreams, guiding the audience through the most memorable storylines in Coronation Street's history and encountering well-loved characters old and new.
Julie Goodyear (Bet Lynch), Kevin Kennedy (Curly Watts), Brian Capron (Richard Hillman), Bill Roache (Ken Barlow) and Katy Cavanagh (Julie Carp) have previously been confirmed for the show.
Following its premiere in Manchester, Street of Dreams will tour to Dublin, Belfast and Newcastle.
> Coronation Street musical is a ten-star show, says Julie Goodyear
> Coronation Street musical is brilliant, says Paul O'Grady
> Coronation Street musical to tour in May
> Read more Coronation Street news and spoilers
Watch a promo for Coronation Street's Street of Dreams musical below: