The Theatre Royal in Bath, England, was built in 1805. A Grade II* listed building, it has been described by the Theatres Trust as "One of the most important surviving examples of Georgian theatre architecture". It has a capacity for an audience of around 900.

The Theatre Royal was built to replace the Old Orchard Street Theatre, funded by a tontine and elaborately decorated. The architect was George Dance the Younger, with John Palmer carrying out much of the work. It opened with a performance of Shakespeare's Richard III and hosted performances by many leading actors of the time including Dorothea Jordan, William Macready and Edmund Kean. A major fire in 1862 destroyed the interior of the building and was quickly followed by a rebuilding programme by Charles J. Phipps, which included the construction of the current entrance. Further redecoration was undertaken in 1892; more extensive building work, including a new staircase and the installation of electric lighting, followed in 1902. Despite performances by casts including Sarah Bernhardt, the ballerina Anna Pavlova and Mrs. Patrick Campbell, the theatre was rarely very profitable. During World War II Donald Wolfit, Irene Vanbrugh, John Gielgud and Sybil Thorndike appeared, with shows including Noël Coward's Private Lives and Blithe Spirit, a performance by Ballet Rambert and light entertainment such as Charley's Aunt, but audiences declined.

In 1979 the theatre was bought by a trust and, following public donations, it underwent refurbishment, with the rebuilding of the stage and the installation of a new taller fly tower for scenery and lighting. In 1997 a new 120-seat theatre, known as the Ustinov Studio, was opened. Further restoration work to the main auditorium was needed in 2010. In 2005 a children's theatre known as The Egg was opened. The complex also includes bars and The Garrick's Head pub.

The theatre was erected in 1805, replacing the Old Orchard Street Theatre which had obtained a royal patent by the Bath Theatre Act 1768 (8 Geo. 3. c. 10) enabling the use of the title 'Theatre Royal', the first to achieve this outside London. The Orchard Street site became a church and is now a Freemason's Hall. The new theatre was first proposed in 1802 at several sites in Bath until the current site was chosen in 1804; funding was raised by the use of a tontine, an investment plan named after the Neapolitan banker Lorenzo de Tonti, who is credited with inventing it in France in 1653. It combined features of a group annuity and a lottery. Each subscriber paid an agreed sum into the fund, and thereafter received an annuity. As members died, their shares devolved to the other participants, and so the value of each annuity increased. On the death of the last member, the scheme was wound up. Shares, which cost £200, were rapidly purchased, with the Prince Regent, who later became George IV, and his brother Prince Frederick among the subscribers. A similar scheme had previously been used for the construction of the Bath Assembly Rooms.

The exterior of the building, with arches, pilasters, garlands and ornaments, which is visible from Beauford Square, was designed by George Dance the Younger who also designed the decorative sections of the interior. The main fabric of the building was by John Palmer, who supervised the construction. The ceiling was decorated with panels from Fonthill Splendens, a mile from Fonthill Abbey, which were painted by Andrea Casali and donated to the theatre by Paul Cobb Methuen. Because of the potential damage from the gas lights, which were installed in 1827, the paintings were moved by William Blathwayt to Dyrham Park.

The opening night was on 12 October 1805 was a production of Richard III, with an unknown actor in the lead. Though not a success, the theatre soon established a good reputation and thrived under the management of William Wyatt Dimond. Early performances included appearances by the child actors Master Betty and Clara Fisher, with adult leads from prominent actors on the London stage including Dorothea Jordan, William Macready and Edmund Kean. In addition to Shakespeare and other serious drama, the productions included opera and comedy with Joseph Grimaldi playing the clown in a pantomime of Mother Goose in November 1815.

Between the 1810s and 1850s there were a series of changes in ownership and management. These coincided with a Puritan revival and a fall in Bath's popularity; reductions in receipts were compounded by rising payments for actors from London. As a result, the theatre underwent financial crises and fell into a period of decline. Fortunes began to improve when James Henry Chute, who was the manager of the Bath Assembly Rooms and the son-in-law of the owner Mrs Macready, took over as the manager of the theatre and once again audiences began to rise.

On 18 April 1862 a major fire destroyed the interior of the building including the stage, scenery, wardrobe and library, leaving just the exterior walls still standing. A new company was formed to rebuild the theatre and a competition held for designs. The winner was C.J. Phipps and rebuilding, which included the new entrance on Sawclose, quickly followed. The present main entrance to the Theatre Royal, in Sawclose, was built in 1720 by Thomas Greenway, and was previously at Beau Nash's house. Pevsner criticizes the mouldings of window-frames, frieze and volutes of the door-hood brackets as "characteristically overdone", and mentions Wood citing its "profuse ornament" which was typical of a mason rather than an architect. Chute remained as manager and employed Charles Kean and Ellen Terry to play in A Midsummer Night's Dream on the opening night, 3 March 1863.