Henley Royal Regatta is a rowing event held every year on the river Thames by the town of Henley-on-Thames, England. It lasts for 5 days (Wednesday to Sunday) over the first weekend in July. Races are head-to-head knock out competitions, raced over a course of 1 mile, 550 yards (2,112 m). The regatta regularly attracts international crews to race. The most prestigious event at the regatta is the Grand Challenge Cup for Men's Eights, which has been awarded since the regatta was first staged.

As the regatta pre-dates any national or international rowing organisation, it has its own rules and organisation, although it is recognised by both the Amateur Rowing Association (the governing body of rowing in England and Wales) and FISA (the International Rowing Federation). The regatta is organised by the Stewards, who are largely former rowers themselves.

The regatta was first staged in 1839 and proved so successful that it was expanded the next year from one day to two the next year. Further expansion to three days in the late 19th century, 4 days in 1906 and five days in 1986 are proof of the regatta's importance.

The regatta has been known as Henley Royal Regatta since 1851, when Prince Albert became the first royal patron. Since his death, every reigning monarch has agreed to be the patron.

The regatta was for male rowers only until 1993 (women had been permitted to cox for some time), when women's single sculls were introduced. Since then women's eights and women's quadruple sculls have also been added. Dueto the increasing number of women rowing in Britain, Henley Women's Regatta was formed in 1988 although the subsequent inclusion of elite-level events at Henley Royal has reduced participation in the top events at Henley Women's somewhat. Henley Women's takes place 3 weeks before Henley Royal.