UK and Australia Sign Long-Term Submarine Deal in Geelong

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The United Kingdom and Australia have formally signed a landmark defence agreement, paving the way for decades of joint collaboration on nuclear-powered submarines. Known as the Geelong Treaty, the bilateral Nuclear‑Powered Submarine Partnership and Collaboration Treaty formalises strategic and industrial defence cooperation between Australia and the UK under AUKUS Pillar I.

Signed on 26 July 2025 during the UK‑Australia Defence Ministers’ Meeting in Geelong, Victoria, the treaty was concluded by Australia’s Deputy Prime Minister and Defence Minister, Richard Marles MP, and the UK’s Secretary of State for Defence, John Healey MP. The agreement represents a 50‑year bilateral commitment under AUKUS Pillar I to jointly design, build, operate, sustain and dispose of the SSN‑AUKUS class of nuclear-powered submarines.

The Geelong Treaty establishes cooperation across the full vessel lifecycle—including design, build, operation, sustainment and disposal—and supports infrastructure, workforce, regulation and skills development for Australia’s SSN‑AUKUS programme, including planned rotational visits by UK Astute‑class submarines to HMAS Stirling under Submarine Rotational Force – West.

“This is a 50‑year commitment,” Mr Marles said, emphasising the strategic ambition of the Geelong Treaty, which “cements the enduring strength of the UK‑Australia defence relationship” and enables delivery of a cutting‑edge undersea capability under SSN‑AUKUS.

Central to the partnership is the introduction of the SSN-AUKUS submarines, a next-generation platform jointly developed by Australia, the UK, and the United States. These submarines, equipped with advanced stealth and strike capabilities, are a core element of the AUKUS (Australia-United Kingdom-United States) security framework aimed at bolstering defence capacity in the Indo-Pacific and Euro-Atlantic regions.

As part of the agreement, a UK Royal Navy Astute-class submarine will maintain a rotational presence at HMAS Stirling in Western Australia under the Submarine Rotational Force-West. This arrangement supports regional stability and enhances allied presence in an increasingly contested Indo-Pacific theatre.

The treaty is fully compliant with international nuclear obligations, including the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the South Pacific Nuclear Free Zone Treaty, and safeguards agreements with the International Atomic Energy Agency (IAEA). It also aligns with the AUKUS Naval Nuclear Propulsion Agreement (ANNPA), ensuring transparency and adherence to international norms.

John Healey MP stated, “The Geelong Treaty will enable the delivery of SSN-AUKUS and resilient trilateral supply chains, supporting port visits and the rotational presence of a UK Astute-class submarine at HMAS Stirling.”

Beyond the strategic and security imperatives, the treaty is expected to deliver economic dividends. Thousands of skilled jobs will be created across both nations, while the defence sectors in Australia and the UK are set to benefit from greater industrial activity, research collaboration, and innovation in advanced manufacturing.

The agreement also signals a united front between trusted allies confronting emerging global threats. With China’s assertive moves in the Indo-Pacific and mounting pressure on Western defence industries, the treaty represents a significant pivot towards hardening collective deterrence.

By setting this in motion, Australia and the UK have sent a clear message: long-term defence readiness, underpinned by trust and shared values, will remain a priority. The Geelong Treaty solidifies bilateral defence cooperation and reinforces a trilateral commitment with the United States under AUKUS to promote peace, stability, and deterrence in key strategic regions.