Mission Specialist Defender Mk IV

The Mission Specialist Defender Mk IV is a remotely operated vehicle (ROV) manufactured in the United States. An ROV is a tethered underwater robot controlled by an operator via a cable, as distinct from an autonomous underwater vehicle (AUV) which executes pre-programmed missions independently. The Defender Mk IV is the fourth-generation variant in Mission Specialist's Defender series, designed for naval and commercial subsea inspection and intervention tasks.

The Mission Specialist Defender Mk IV was named on 30 May 2026 as one of two platform systems in the AUKUS Pillar II Signature Project, alongside the L3Harris Iver4 900 AUV. Both named systems are US-built. The Signature Project targets mine countermeasures (MCM), anti-submarine warfare (ASW), seabed-infrastructure protection, and contested-littoral manoeuvre, with hardware deliveries beginning in 2027.

The ROV's selection alongside a torpedo-tube-launched AUV reflects complementary roles: the Iver4 900 deploys from submarines for clandestine forward operations, while a larger ROV platform can support seabed-infrastructure inspection and intervention from surface ships. No budget figure, unit quantities, or deployment configurations were disclosed in the AUKUS fact sheet.