English National Opera (ENO) is a British opera company based in London, resident at the London Coliseum in St Martin's Lane. It is one of the two principal opera companies in London, along with The Royal Opera. ENO's productions are sung in English.

The company's origins were in the late 19th century, when the philanthropist Emma Cons, later assisted by her niece Lilian Baylis, presented theatrical and operatic performances at the Old Vic, for the benefit of local people. Baylis subsequently built up both the opera and the theatre companies, and later added a ballet company; these evolved into the ENO, the Royal National Theatre and The Royal Ballet, respectively.

Baylis acquired and rebuilt the Sadler's Wells theatre in north London, a larger house, better suited to opera than the Old Vic. The opera company grew there into a permanent ensemble in the 1930s. During the Second World War, the theatre was closed and the company toured British towns and cities. After the war, the company returned to its home, but it continued to expand and improve. By the 1960s, a larger theatre was needed. In 1968, the company moved to the London Coliseum and adopted its present name in 1974.

Among the conductors associated with the company have been Colin Davis, Reginald Goodall, Charles Mackerras, Mark Elder and Edward Gardner. The current music director of the ENO is Martyn Brabbins. Noted directors who have staged productions at the ENO have included David Pountney, Jonathan Miller, Nicholas Hytner, Phyllida Lloyd and Calixto Bieito. The ENO's current artistic director is Annilese Miskimmon. In addition to the core operatic repertoire, the company has presented a wide range of works, from early operas by Monteverdi to new commissions, operetta and Broadway shows.