Sydney is the Australian city where Biocyte Pharmaceuticals has its headquarters in Mission: Impossible 2.
Biocyte is the company connected to Chimera, a genetically engineered virus developed by scientist Nekhorvich. Ethan Hunt’s mission is to stop former IMF agent Sean Ambrose from obtaining the virus and exploiting its cure, Bellerophon.
The film uses Sydney as an important setting for its corporate and laboratory sequences, while other scenes take place in locations including Spain and the Australian countryside. The city’s presence helps establish the film’s international scale and its biotechnology-centered plot.
Sydney can be confused with other Australian cities shown or mentioned in action films, but the question specifically concerns Biocyte’s headquarters. Mission: Impossible 2 was directed by John Woo and released in 2000.