The English Chamber Orchestra (ECO) is a British chamber orchestra based in London. The full orchestra regularly plays concerts at Cadogan Hall, and the ECO Ensemble performs at Wigmore Hall. The orchestra regularly tours in the UK and internationally, and holds the distinction of not only having the most extensive discography of any chamber orchestra, but also of being the most well-travelled orchestra in the world; no other orchestra has played concerts in as many different countries as the ECO.

The ECO has its roots in the Goldsbrough Orchestra, founded in 1948 by Lawrence Leonard and Arnold Goldsbrough. The group took its current name in 1960, when it expanded its repertoire beyond the Baroque period for the first time. Its repertoire remained limited by the group's size, which has stayed fairly consistently at around the size of an orchestra of Mozart's time.