The Capitol of Puerto Rico, also known as Casa de las Leyes (House of Laws), and most commonly referred to as El Capitolio (The Capitol), is the seat of the Legislative Assembly, the bicameral legislature, composed of the Senate and House of Representatives, responsible for the legislative branch of the government of Puerto Rico. Located on San Juan Islet immediately outside the Walls of Old San Juan, the oceanfront, neoclassical Beaux-Arts-style, entirely white marble-covered edifice was constructed between 1921 and 1929 to resemble the ancient Roman Pantheon in Rome, using as inspiration the Low Memorial Library in New York City. It was added to the National Register of Historic Places in 1977.

The Senate of Puerto Rico is the upper house of the Legislative Assembly of Puerto Rico, the territorial legislature of Puerto Rico. The Senate, together with the House of Representatives of Puerto Rico, control the legislative branch of the government of Puerto Rico.