The country will build dozens of the "extra large" autonomous drones for the Royal Australian Navy, with the first entering service in January, Defence Minister Richard Marles said.

"This is a profoundly important capability for the Royal Australian Navy," he told reporters.

Anduril Australia secured a Aus$1.7 billion (US$1.1 billion) contract to build, maintain and develop the new drones.

"We have consistently articulated that Australia faces the most complex, in some ways, the most threatening strategic landscape that we have had since the end of the Second World War," Marles said.

The undersea vehicles will complement Australia's plan to acquire stealthy nuclear-powered submarines in a multi-billion-dollar agreement with Britain and the United States, he said.