The news was announced on the US superstar's Twitter account on Thursday morning.
Sharing a short video of herself performing, Ross, 75, wrote: "This is a dream come true.
"To all the fans across the world, this is my tribute to you. I'm coming to Glastonbury, with love."
— Ms. Ross (@DianaRoss)October 10, 2019
The festival tweeted: “We are delighted to announce that Diana Ross will play the Sunday legends slot on the Pyramid Stage at Glastonbury 2020.”
Glastonbury festival organiser Emily Eavis said: “I am delighted to say that one of the all-time greats, the wonderful Diana Ross, is coming to Glastonbury to play the Sunday legend slot on the Pyramid next year”.
I am delighted to say that one of the all-time greats, the wonderful Diana Ross, is coming to Glastonbury to play the Sunday legend slot on the Pyramid next year.— Emily Eavis (@emilyeavis)October 10, 2019
The soul star who made her name in The Supremes, will perform in the Sunday afternoon slot which has previously played host to icons including Dolly Parton, Lionel Richie and Kylie Minogue.
During her performance at this year's event, Minogue was joined by guests including Nick Cave and Chris Martin.
Tickets for the 2020 event sold out in less than an hour last week.
Fans have two more chances to buy them, thanks to an ongoing ballot which will see another 100 tickets offered sale and the annual resale, taking place in April 2020.