AUKUS submarine (SSN-A) programme

AUKUS is a defence and security partnership between Australia, the United Kingdom and the United States, announced in September 2021.

A major part of the agreement (pillar 1) is to support Australia in acquiring its first conventionally armed, nuclear-powered submarine fleet. It does not involve the transfer of nuclear weapons to Australia.

In a Joint Statement on 13 March 2023 the AUKUS nations set out how pillar 1 of the agreement would be achieved:

• SSN-AUKUS (also referred to as SSN-A in the UK) will be based on the UK’s next-generation submarine design. That design will incorporate technologies from all three nations, including cutting edge US submarine technologies.
• The submarines will be built in the UK and Australia and work will begin by 2030, with a view to entering service toward the end of the 2030s (UK) and the early 2040s (Australia). In the interim, the US will transfer three Virginia-class SSN to Australia in the early 2030s, with potential for the sale of a further two.
• The UK and Australia will both operate the SSN-AUKUS as their conventionally armed attack submarine, equipped for intelligence, surveillance, undersea warfare and strike missions.

The UK currently has two submarine programmes underway: the conventionally armed Astute class attack submarine (SSN), and the Dreadnought class SSBN, which will provide the platform for the UK’s strategic nuclear deterrent from the early 2030s. The last of the Astute class SSN is expected into service by 2026; while construction on the Dreadnought class is expected to continue well into the 2030s.

SSN-AUKUS will be the next generation successor to the current Astute-class SSN. In the Strategic Defence Review, published in June 2025, the government confirmed that it will acquire a fleet of up to 12 SSN-AUKUS submarines. An associated overall cost for the programme has not been provided by the government. At its peak the SSN-AUKUS programme is expected to sustain 21,000 jobs in the UK.

In July 2025, the UK and Australia signed a 50-year bilateral AUKUS partnership treaty which will establish the strategic and operational framework for the design, build and delivery of the AUKUS submarines. At the time of writing, the text of that treaty has not yet been laid before Parliament.

In June 2025, the US said that it was conducting a review of the AUKUS agreement, which has led to speculation that pillar 1 of the agreement could be revised.