MotoGP rights holders Dorna said in a statement that the deal secured the immediate future of the British round after the termination of an agreement with the unbuilt Circuit of Wales.
Silverstone has hosted MotoGP since 2010, most recently as part of an agreement with the Circuit of Wales that secured a five-year deal with Dorna from 2015-19 but failed to get the necessary funding.
"A lot of time and money has been invested in recent years to ensure MotoGP fans, teams and riders enjoy what Silverstone has to offer and we are delighted to have secured the contract to 2020," said Silverstone managing director Stuart Pringle.
"Two-wheel racing is as much a part of Silverstone's heritage as four-wheel racing and we are looking forward to welcoming the Championship and its fans back to Silverstone next August."
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Silverstone also hosts the country's Formula One Grand Prix but the future of that race after 2019 remains uncertain after the circuit this year activated a break clause in its contract.
The circuit has the biggest attendance of any Formula One grand prix, with a four-day total of 300,000 in 2017, but MotoGP crowds are far lower with only 56,000 on race day this year.
Dorna chief executive Carmelo Ezpeleta said Britain was important to a series currently dominated by Italian and Spanish riders.
"The United Kingdom is an important market for Dorna and has to remain on the MotoGP calendar, especially with the introduction of the British Talent Cup next year," he said.
(Reporting by Alan Baldwin, editing by Neil Robinson)
