The five metal detectorists who found the coins will split the proceeds with the landowner.
A hoard of 2,584 silver pennies from the time of the Norman Conquest has been bought for £4.3m ($5.6m) - making it the highest-value treasure ever found in the UK.
The South West Heritage Trust has bought the "unprecedented" hoard of coins from the Crown.
Sam Astill, chief executive of the Trust, said: “The hoard symbolises a pivotal moment in English history, and we are delighted to have made this acquisition so that it may be enjoyed by generations to come."
The Chew Valley Hoard, as it is now known, was discovered on 26 January 2019 by seven finders while they were metal detecting in the Chew Valley area of Bath and North East Somerset, in south west England. It is the largest hoard found in the UK from the period after the Norman Conquest.
Experts suspect the coins were likely buried for safekeeping in the turmoil of the Norman Conquest. Represented on just under half the coins is Harold II (1066), the last crowned Saxon king of England, and the other half feature William I (1066-1087).
Heritage Minister Sir Chris Bryant said: “This remarkable hoard gives us unique insight into our country's rich history and one of the most important moments in our history, when these islands were thrown into turmoil by the Norman Conquest.”
From 26 November, the coins will go on display at the British Museum.