The Princess Theatre, originally Princess's Theatre, is a 1452-seat theatre in Melbourne, Victoria, Australia. Established in 1854 and rebuilt in 1886 to a design by noted Melbourne architect William Pitt, it is the oldest surviving entertainment site on mainland Australia. Built in an elaborate Second Empire style, it reflects the opulence of the "Marvellous Melbourne" boom period, and had a number of innovative features, including state of the art electric stage lighting and the world's first sliding ceiling, which was rolled back on warm nights to give the effect of an open-air theatre.

William Pitt was an Australian architect and politician. Pitt is best known as one of the outstanding architects of the "boom" era of the 1880s in Melbourne, designing some of the city's most elaborate High Victorian commercial buildings. He worked in a range of styles including Gothic Revival, Italianate, French Second Empire, and his own inventive eclectic compositions. He had a notable second career after the crash of the 1890s, becoming a specialist in theatres and industrial buildings.