The Isaac Theatre Royal (formerly known as the Theatre Royal) is a heritage building in Christchurch, New Zealand, designed by brothers Sidney and Alfred Luttrell.^[2] Built in 1908, it is the only operational Edwardian-style theatre remaining in New Zealand.^[3]

The current Theatre Royal is the third theatre of its name on Gloucester Street. The first theatre, built in 1861, was on a site across the road from the current Theatre Royal. It was originally called the Canterbury Music Hall.^[2] That building was replaced by a newer theatre on the same site in 1876. Five years after the new theatre was completed it was renamed the Theatre Royal.^[4] When the current theatre was built in 1908 the old theatre across the road was sold to The Press, which owned it up until the Canterbury earthquakes.^[5][2]

In 1928 the theatre was refitted as a cinema. During the refit the current marble staircase replaced the original wooden one.^[2] Significant structural earthquake strengthening was carried out in 1999 and 2000.^[6][7] Between 2004 and 2005 major work was done to the theatre over a nine-month period at a cost of $6.2 million.^[6][4] The whole backstage was demolished to make room for a modern concrete fly tower and dressing room facilities. The Proscenium arch was also widened by 1.5m and the stage and fly tower were made wider and deeper.^[6] The facilities within the existing front of house areas were also upgraded.^[6] It was during the 2004/5 renovation that the theatre became the Isaac Theatre Royal, to honour supporter Lady Diana Isaac.^[4]

The 1908 auditorium and foyer sustained considerable damage during the February 2011 Christchurch earthquake and the June aftershock.^[1] The Theatre was closed for nearly four years while the restoration took place. At a cost of $40 million the Theatre was completely restored and brought up to current building code requirements.^[8] All of the significant architectural elements were rescued and restored by skilled craftsmen; including a completely rebuilt auditorium dome made from carbon fibre using the original 1908 painted mural by Studio Carolina Izzo.^[8] The newly restored Theatre opened on 17 November 2014.^[6]