Giulio Cesare is an Italian opera by George Frideric Handel. The libretto was written by Nicola Frecesco Haym. It was first performed in London on February 20, 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 oblivion in the 19th century.

In the 20th century, it was revived (in heavily altered form) in Göttingen in 1922. In modern times, it has proven be by far the most popular of Handel's operas, with more than two hundred productions in many countries. The title role and the roles of Sextus and Ptolemy were written for castrati, and in modern productions, Giulio is either transposed for baritone or sung by a contralto or, more frequently in recent years, a countertenor. Sextus is usually sung by a mezzo-soprano and Ptolemy by a countertenor.

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 has become part of the standard operatic repertoire. There are several recordings of it, and it is regularly performed.