The massive 1,111 carat rock, which is the size of a fist, was found by Lucara Diamond Corp at its mine in Karowe, and is the second biggest ever found.
It is the biggest diamond to be found on earth in more than 100 years and is only pipped to the top spot of all time by the mammoth 3,106-carat Cullinan which was found in South Africa in 1905 and ended up cut into pieces - many of which are in the British Crown Jewels.
William Lamb, president of Lucara, said: "This historic diamond recovery puts Lucara and the Karowe mine amongst a select number of truly exceptional diamond producers.
"The significance of the recovery of a gem quality stone larger than 1,000 carats, the largest for more than a century and the continued recovery of high quality stones from the south lobe, cannot be overstated.
The Lucara diamond, which measures 65mm x 56mm x 40mm, is around 1,000 times the size of the average engagement ring.
It is a Type IIa, which is the rarest and purest diamond. Just two per cent of diamonds are Type IIa, suggesting the gemstone's value will be enormous.
Amazingly, two other large stones were also found by the company - one 813 carat and the other 374 carat.
The giant stone is yet to be valued but experts predicted the stone had "the potential to be one very expensive diamond."
Vadim Weinig, a third generation diamond dealer and co-founder of online jewellers 77Diamonds.com, said it had the potential to break all price records if sold.
He said: "It has taken over 100 years to unearth a diamond of this size so this is a very exciting find.
"I'm not convinced we will find another diamond of this size and quality in even the next 200 years.
"They (Lucara Diamond Corp) will be thrilled on many levels as will the Government of Botswana, because diamonds have transformed the economy of Botswana and dramatically improved the lives its inhabitants.
"If the owners that cut this diamond achieve a pure stone - known as D Flawless - of close to a third of the size of the rough, which should be possible, this would produce the largest pure diamond in the world and would likely break all known records if sold."
Mr Weinig said the main factors which will determine the price of the diamond are its colour, its clarity and its shape.
He added: "It will be impossible to speculate until the diamond has been closely studied, but we already know this is a Type IIa diamond, one of the rarest and most sought after types."
The most expensive diamond on record is the Blue Moon Josephine, which was sold last week by Sotheby's for £31.9 million.