BAE Systems employs about 5,000 people in the UK to build the fighter jets, mainly at Warton in Lancashire.
Qatar's purchase of 24 jets includes a support and training package from BAE, with deliveries due to start in 2022.
The deal was announced in Doha by Defence Secretary Gavin Williamson and his Qatari counterpart, Khalid bin Mohammed al Attiyah.
Mr Williamson said it was a "massive vote of confidence, supporting thousands of British jobs and injecting billions into our economy".
BAE chief executive Charles Woodburn said the contract, worth £5bn to the company, was the start of a long-term relationship with Qatar and its armed forces.
"This agreement is a strong endorsement of Typhoon's leading capabilities and underlines BAE Systems' long track record of working in successful partnership with our customers," he said.
The Typhoon entered service with the RAF in 2007 to replace the ageing Tornado fleet.
Although the Qatar order secures the production of the Typhoon at BAE into the next decade, it will not stop the 2,000 job cuts announced in October from going ahead.