The Acheron class (officially re-designated as the I class in October 1913) was a class of twenty-three destroyers of the British Royal Navy, all built under the 1910-11 Programme and completed between 1911 and 1912, which served during World War I. A further six ships were built to the same design for the Royal Australian Navy as River-class destroyers. There was considerable variation between the design and construction of ships within this class, which should be considered as more of a post-build grouping than a homogeneous class.