Teatro di San Carlo is an opera house located in Naples, Italy. It was inaugurated on November 4, 1737, and is the oldest continuously active opera house in the world. The theater was designed by architect Giovanni Antonio Medrano and built by King Charles III of Naples as a replacement for the previous theater that had been destroyed by fire. The new theater was named after the King's patron saint, Saint Charles Borromeo.

The Teatro di San Carlo has a seating capacity of about 1,400 people and is renowned for its excellent acoustics. The interior is decorated with elaborate frescoes and features a horseshoe-shaped auditorium with six tiers of boxes, adorned with gold leaf and stucco decorations.

Throughout its history, the Teatro di San Carlo has hosted many of the greatest operatic performers, composers, and conductors of all time. Some of the world's most famous operas have premiered at the theater, including Gioachino Rossini's "The Barber of Seville" and Gaetano Donizetti's "Lucia di Lammermoor."

Today, the Teatro di San Carlo is still a major venue for opera, ballet, and other musical performances. Its rich history, unique design, and excellent acoustics continue to make it a cultural icon of Naples and one of the most important opera houses in the world.