Joining Everett in the principal cast will be Joshua McGuire - currently appearing in Privacy at the Donmar Warehouse - as Mozart, alongside Jessie Buckley, recently seen opposite Jude Law in Henry V, as Mozart's wife Constanze Weber.
Also confirmed for the Amadeus cast is John Standing as Count Franz Orsini-Rosenberg, Simon Jones as Joseph II Emperor of Austria, Richard Clifford as Baron Gottfried van Swieten and Timothy Kightley as Count Johann Killian von Strack.
Amadeus will be the first production staged in the newly refurbished Festival Theatre, which reopens this summer following a £22 million redevelopment.
Also announced today is that Jonathan Coy (Chichester's A Month in the Country), Paul Ready (Wastwater, Royal Court) and Marcia Warren (The Ladykillers, West End) will join Rosalie Craig and Shaun Evans in the Miss Julie / Black Comedy double-bill, which runs in the Minerva Theatre from 4 July to 9 August.
And Paulette Randall, who recently directed the award-winning revival of Fences starring Lenny Henry, will helm a revival of Terrence McNally's 1987 play Frankie and Johnny in the Clair De Lune, running from 6 November to 6 December in the Minerva.