The band have been added to the line-up of the Summer Sessions festival.
The event, which was launched in 2018, will return to the Ross Bandstand for the first time in three years in August.
Lionel Richie, Michael Kiwanuka, Tom Jones, Simple Minds and Travis - who were all due to appear in 2020 - will all be performing during the event, which will coincide with the first full week of the Fringe.
The rescheduled dates for the festival have been confirmed weeks after organisers of the Royal Edinburgh Military Tattoo revealed plans to return with a revamped show in August.
Basement Jazz will be headlining Edinburgh’s Hogmanay festival with a show at the Ross Bandstand.
An official announcement about the Summer Sessions states: “With over 50 million albums sold worldwide, four of which were No 1 in the UK, Simply Red are the true champions of blue-eyed soul.
“Singer and songwriter Mick Hucknall was described by Q magazine as having ‘the most prodigious voice this side of Motown’ and there is no denying the emotion he conveys in his captivating performances.
“Next summer, the band bring their amazing live show and incredible catalogue of hits to the capital, where Edinburgh Castle will provide a stunning backdrop to an unforgettable night under the ‘Stars’.”
The week-long Summer Sessions festival will get underway on 7 August with Richie’s concert while Travis will bring the event to an end a week later.
A pre-sale for tickets is opening this Thursday, with tickets on general sale on Friday.