The term blue-water navy is a colloquialism used to describe a maritime force capable of operating across the deep waters of open oceans. While what actually constitutes such a force remains undefined, there is a requirement for the ability to exercise sea control at wide ranges.

Blue-water capability means that a fleet is able to operate on the high seas, but there is no agreed definition of the term. It implies force protection from sub-surface, surface and airborne threats and a sustainable logistic reach, allowing a persistent presence at range. A hallmark of a true blue-water navy is the ability to replenish at sea, and the commissioning of underway replenishment ships is a strong sign of a navy's blue-water ambitions.

However in public discourse, blue-water capability is identified with the operation of iconic capital ships such as battleships and aircraft carriers. For instance, during the debate in the 1970s whether Australia should replace HMAS Melbourne, a former Chief of Navy claimed that if Australia did not replace her last aircraft carrier, she "would no longer have a blue-water navy". In the end Australia did not buy a new carrier, but former Parliamentary defence advisor Gary Brown could still claim in 2004 that her navy remained "an effective blue-water force". The Soviet Navy towards the end of the Cold War is another example of a blue-water navy that had minimal carrier aviation, relying instead on submarines, missile-carrying surface ships, and long-range bombers based on land.

Bluewater or Blue Water may refer to: