The River-class destroyer (re-designated in 1913 as the E class) was a class of torpedo boat destroyer built for the Royal Navy in the first few years of the 20th century, and which saw extensive service in World War I. These 37 vessels (33 formally ordered under three annual construction programmes, plus another three built on speculation and then purchased by the Admiralty, and a final unit building in Italy for the Portuguese Navy and purchased in 1915) were all constructed to disparate builders' designs, just like the preceding classes.

The class introduced new features to destroyer design, placing a greater emphasis on seakeeping and endurance and less on a high maximum speed in good weather. All the ships were named after British, Irish and Portuguese rivers, and as such were the first Royal Navy destroyer class to be named systematically.

The concept for the River class began in December 1900, with a request from Commander John Michael de Robeck, then the senior destroyer officer in the Mediterranean Fleet, for a new class of destroyer with a longer range and better sea-keeping qualities than the existing "27-knotter" class (the survivors of which would be redesignated the A-class in 1913) and "30-knotter" class (redesignated the B, C and, D classes in 1913). De Robeck's specification called for a range of 1,650 nmi (3,056 km) at a sustained speed of 18 knots (33 km/h); the "30-knotter" could only make 1,400 nmi (2,593 km) at its cruising speed of 13 knots (24 km/h).

De Robeck also called for various modifications to destroyer design to help make ships more seaworthy, in particular keeping up their speed in adverse weather conditions. The most noticeable change would be to introduce a raised forecastle rather than an arched turtleback for the hull forward of the bridge, and that the bridge should be placed further aft to keep it clear of spray from waves breaking over the bow. Furthermore, he felt that destroyers should run their speed trials with a more realistic load of fuel and supplies. The "30-knotter" type might have a nominal speed of 30 knots, but even in very good weather this was never achieved in service.

Other officers serving on Royal Navy destroyers made similar observations about their ships. John de Robeck's commanding officer, Vice-Admiral "Jackie" Fisher, drew a comparison with the German S90-class torpedo boat, which had impressed Royal Navy officers who had seen it.

In July 1901 the Director of Naval Construction worked on sketch designs for future destroyers, which included many of the features de Robeck and his colleagues advocated, as well as a heavier and more reliable kind of engine. The trials speed was initially 27 knots (50 km/h), though further requirements for increased strength reduced the speed to 25.5 knots (47.2 km/h). While this speed seemed like a significant reduction, it would be measured with a realistic 95 tons of coal loaded on board, and the better sea-keeping properties meant that the new ships would perform better than a "30-knotter" in any seas except for a flat calm.

As with other early British destroyer classes, the Admiralty invited specialist private firms to submit their own designs for destroyers which would meet the specification. The idea was to use the builders' knowledge of building small, fast, ships to help cram powerful machinery into a small hull. For this reason, details of the hull and internal arrangements differed between ships in the class.

Nevertheless, the River class can clearly be distinguished from previous destroyers because of its raised forecastle. Previous British designs had a low "turtle-back" forecastle, which, although intended to clear the bows, caused them to dig in to the sea, resulting in a very wet conning position. The bridge was also further back than in previous destroyer models.