The Philharmonia is an orchestra based in London. Since 1995 it has been based in the Royal Festival Hall. In Britain it is also the Resident Orchestra at De Montfort Hall, Leicester and the Bedford Corn Exchange.

The orchestra was founded in 1945 by Walter Legge, and although it did give the occasional live concert, it was mainly intended to be a recording orchestra for EMI, where Legge was an executive. Thomas Beecham led its debut concert in 1946, but he was ruled out as a long-term conductor of the group when he tried to take control of the orchestra and change its name (Beecham instead went on to found his own Royal Philharmonic Orchestra).

In its early years, many prominent conductors made recordings with the ensemble, including Arturo Toscanini and Wilhelm Furtwängler. However it was Herbert von Karajan (who was not allowed to work in Germany or Austria at the time because of his Nazi record) who was most associated with the Philharmonia in its early years. Karajan built the orchestra into one of the finest ensembles in the world, and made numerous recordings, including all the Beethoven symphonies.

The Philharmonia is the most recorded orchestra in the world, with over one thousand recordings. It has also been heard on the soundtracks of many films, performing the musical scores of such classics as Laurence Olivier's 1944 film version of Shakespeare's Henry V, and David Lean's film version of Oliver Twist (1948).