Stockholm has had two opera houses with the name of Royal Opera:
The Gustavian Opera
The original Stockholm Opera, the work of architect Carl Fredrik Adelkrantz was commissioned by King Gustav III in 1775, and the first performance was in 1782. The king was a strong adherent of the ideal of an "enlightened monarchy" and as such was a great patron of the arts. Coincidentally, it was at the opera house which he had built that the king was to meet his fate. During a masquerade at the Opera on the 16 of March 1792, he was shot by Jacob Johan Anckarström, and died several days later. (In turn, this event inspired the opera Un Ballo in Maschera by Verdi)
The Oscarian Opera
The old opera served for another century, when it was demolished in 1892 to give way to construction of a new Opera by Axel Johan Anderberg, finished seven years later and inaugurated by king Oscar II.
Both opera houses are officially the "Royal Opera", however the terms "The Gustavian Opera" and "The Oscarian Opera", or the "Old" and "New" Opera are used when distinction is needed.