Harland & Wolff, the Belfast shipyard best known for the Titanic, has been saved by a deal with Spain's state-owned shipbuilder.
Navantia had been in exclusive negotiations since October after Harland & Wolff's holding company fell into administration.
About 1,000 jobs are to be saved in the deal, which also includes Harland & Wolff's facilities in Scotland and England.
The UK Business Secretary Jonathan Reynolds said the deal was "good for jobs" and "good for national security".
Navantia, which is 100% owned by Spain's government, has been a significant recipient of funding from the European Commission as part of the European Defence Fund.
Joining the fund is a possible objective for the UK-EU security reset, set to be discussed at a summit early in the new year.
The Spanish economy minister responsible for its state-owned businesses, Carlos Cuerpo, met with Chancellor Rachel Reeves and Business Secretary Jonathan Reynolds in London last month.
Navantia already has a business relationship with Harland & Wolff. It is the main contractor on a project to build three support ships for the Royal Navy, with Harland & Wolff acting as UK subcontractor.
The company employs a core staff of about 1,000 in Belfast, Appledore in England and Methil and Arnish in Scotland.
Navantia's main shipyard is at Cadiz in southern Spain.
It employs more than 4,000 people and has an annual turnover of about €1.3bn (£835m).
For some people, a takeover by Spain's national shipbuilder will represent another example of the UK's industrial decline.
For the Harland & Wolff workforce, it is probably the best possible result.
In 2019, the company's Norwegian owner decided the shipyard didn't have a future and it was placed into administration.
It was then bought by a UK company which had ambition but lacked money and expertise.
Now it is heading into the ownership of an established shipbuilder which has the financial backing of the Spanish state.
Harland & Wolff was founded in 1861 by Yorkshireman Edward Harland and his German business partner, Gustav Wolff.
By the early 20th Century, Harland & Wolff dominated global shipbuilding and had become the most prolific builder of ocean liners in the world.
However, in the period since World War Two it has lurched from crisis to crisis and was under UK state control from 1977 to 1989.
In 2019, its then Norwegian owners withdrew financial support and the business fell into insolvency, having not built a ship in a generation.
It was bought by InfraStrata, a small London-based energy firm which did not have significant experience in marine engineering.
InfraStrata later changed its name to Harland & Wolff and in 2022 won the Royal Navy contract as part of a consortium led by Navantia.
However, financial losses mounted as it scaled up its operations and it became increasingly reliant on high-interest borrowings from a specialist US lender, Riverstone.
The company sought a £200m government loan guarantee to refinance its borrowings but that was rejected for being too risky for taxpayers.
Its holding company entered administration in September and restructuring expert Russell Downs was appointed to run the business and find a new owner.