The trio join the first wave of acts announced for the annual family-friendly event held at of Henham Park, Suffolk between July 12 and July 15.
alt-J, who will close the festival on the final night, said: ''We are over the moon to be returning to Latitude for a fourth time. It's a festival that's nurtured us beyond any other, taking us from the Lake Stage to the 6music Stage and then to headlining in 2015. To do so again is a huge privilege. See you in Suffolk!''
Solange - who is the younger sister of R&B superstar Beyonce - has been riding high on the success of her critically-acclaimed LP 'A Seat at the Table', and will perform her first -ever festival headline slot at Latitude playing Friday night.
Whilst Brandon Flowers and co will also pop their Latitude-headlining cherry this summer headlining the Saturday.
Also performing over the four dates are The Vaccines, Wolf Alice, Rag'n'Bone Man, James, Mogwai, Jon Hopkins, The Charlatans, Benjamin Clementine and Jessie Ware.
It follows on from 2017, which saw The 1975, Mumford & Sons and Fleet Foxes headline.
As well as a stellar music line-up, the four days will also see an abundance of comedy stars entertain the masses.
TV legend Harry Hill has been announced for the comedy and theatre arena.
He said: ''I like latitude, I like longitude, but which is better? There's only one way to find out - play the comedy arena at Latitude! I can't wait!''
Many more acts are set to be announced in the coming weeks.
Tickets are on sale now from www.latitudefestival.com