Giulio Cesare in Egitto (Julius Caesar in Egypt, HWV 17), commonly known simply as Giulio Cesare, is an Italian opera (dramma per musica) in three acts composed for the Royal Academy of Music by George Frideric Handel in 1724. The libretto was written by Nicola Francesco Haym who used an earlier libretto by Giacomo Francesco Bussani, which had been set to music by Antonio Sartorio (1676).

It was first performed at the King's Theatre in Haymarket, London on 20 February 1724. The opera was an immediate success. Handel revived it (with changes) in 1725, 1730, and 1732; it was also performed in Paris, Hamburg, and Brunswick. Like Handel's other works in the opera seria genre, Giulio Cesare fell into obscurity in the 19th century.

The roles of Cesare and Cleopatra, sung by the castrato Senesino and famous soprano Francesca Cuzzoni respectively, and which encompass eight arias and two recitatives accompagnati each, make full use of the vocal capabilities of the singers. Cornelia and Sesto are more static characters because they are completely taken by their primary emotions, she with pain because of her husband's death and constantly constrained to defend herself from the advances of Achilla and Tolomeo, and he consumed by vengeance for his father's death.

Cleopatra, on the other hand, is a multifaceted character: she uses at first her womanly wiles to seduce Cesare and gain the throne of Egypt, and then becomes totally engaged in the love affair with Cesare. She has great arias of immense dramatic intensity Se pietà di me non senti (II, 8) and Piangerò la sorte mia (III, 3). Her sensual character is described magnificently in the aria V'adoro, pupille, in which Cleopatra, in the guise of Lidia, appears to Cesare surrounded by the Muses of Parnassus (II, 2). This number calls for two orchestras: one is an ensemble scene with strings with sordino, oboe, tiorba, harp, bassoons and viola da gamba concertante.

Curio and Nireno do not get any arias in the original version, only singing recitatives, though they take part in the first and final choruses. However, Handel composed an aria for Nireno for a later revival in 1730.

In the 20th century, the opera was revived (in heavily altered form – reorchestrated and revamped with the male castrato roles transposed down for a baritone, tenor or bass) in Göttingen in 1922 by the Handel enthusiast Oskar Hagen. Hans Knappertsbusch and Karl Böhm both conducted it in Munich in 1923, and its first American performance took place at the Smith College of Music in Northampton, Massachusetts, in 1927. The first British revival of a Handel opera was the staging of Giulio Cesare at the Scala Theatre in London in 1930, by the London Festival Opera Company, singing in English. The young Herbert von Karajan conducted a production in Ulm in 1933. It has subsequently proven to be by far the most popular of Handel's operas, with more than two hundred productions in many countries.

In modern productions, the title role, written for a castrato, is sung by a contralto, mezzo-soprano, or, more frequently in recent years, a countertenor. The roles of Tolomeo and Nireno are normally sung by countertenors. The role of Sesto, written for a soprano, is now usually sung by a mezzo-soprano.

The work is considered by many to be Handel's finest Italian opera, possibly even the best in the history of opera seria. It is admired for its superb vocal writing, its dramatic impact, and its deft orchestral arrangements.

Giulio Cesare is now regularly performed.