The High Seas Fleet (Hochseeflotte) was the battle fleet of the German Imperial Navy and saw action during World War I. The formation was created in February 1907, when the Home Fleet (Heimatflotte) was renamed as the High Seas Fleet. Admiral Alfred von Tirpitz was the architect of the fleet; he envisioned a force powerful enough to challenge the Royal Navy's predominance. Kaiser Wilhelm II, the emperor of Germany, championed the fleet as the instrument by which he would seize overseas possessions and make Germany a global power. By concentrating a powerful battle fleet in the North Sea while the Royal Navy was required to disperse its forces around the British Empire, Tirpitz believed Germany could achieve a balance of force that could seriously damage British naval hegemony. This was the heart of Tirpitz's "Risk Theory," which held that Britain would not challenge Germany if the latter's fleet posed such a significant threat to its own.

The primary component of the Fleet was its battleships, typically organized in eight-ship squadrons, though it also contained various other formations, including the I Scouting Group. At its creation in 1907, the High Seas Fleet consisted of two squadrons of battleships, and by 1914, a third squadron had been added. The dreadnought revolution in 1906 greatly affected the composition of the fleet; the twenty-four pre-dreadnoughts in the fleet were rendered obsolete and required replacement. Enough dreadnoughts for two full squadrons were completed by the outbreak of war in mid 1914; the eight most modern pre-dreadnoughts were used to constitute a third squadron. Two additional squadrons of older vessels were mobilized at the onset of hostilities, though by the end of the conflict, these formations were disbanded.

The terms international waters or trans-boundary waters apply where any of the following types of bodies of water (or their drainage basins) transcend international boundaries: oceans, large marine ecosystems, enclosed or semi-enclosed regional seas and estuaries, rivers, lakes, groundwater systems (aquifers), and wetlands.

Oceans, seas, and waters outside of national jurisdiction are also referred to as the high seas or, in Latin, mare liberum (meaning free seas).

Ships sailing the high seas are generally under the jurisdiction of the flag state; (if there is one) however, when a ship is involved in certain criminal acts, such as piracy, any nation can exercise jurisdiction under the doctrine of universal jurisdiction. International waters can be contrasted with internal waters, territorial waters and exclusive economic zone.

Several international treaties have established freedom of navigation on semi-enclosed seas.

Other international treaties have opened up rivers, which are not traditionally international waterways.