Botswanan diamond firm Debswana said Wednesday it had unearthed a 1 098-carat stone that it described as the third largest of its kind in the world.
The stone, found on 1 June, was shown to President Mokgweetsi Masisi in the capital Gaborone.
"It is believed to be the third largest gem-quality find in the world," said Debswana Managing Director Lynette Armstrong.
The "rare and extraordinary stone... means so much in the context of diamonds and Botswana," she said. "It brings hope to the nation that is struggling."
It also the biggest stone of gem quality to be recovered in the history of the company, a joint venture between the government and global diamond giant De Beers.
The biggest diamond ever discovered in the world was the 3 106-carat Cullinan, found in South Africa in 1905.
The second largest was 1 109-carat Lesedi La Rona - a diamond the size of a tennis ball, discovered at Karowe, north eastern Botswana, in 2015.
Botswana is Africa's leading diamond producer.