In almost a word – every continent except the Antarctica.
Orchids are amazing, we expect to find them in the tropics but they can be found anywhere from the cold climes of Alaska to the semi-arid edge of the Australian deserts.
An Interactive Key to Australian Orchid Genera has an excellent chapter on habitats of Australian orchids.
15 habitats are listed with a list of the type of orchid likely to be found there. The vast majority of Australian terrestrial orchids are found in either lowland (less than 500 metres altitude), in coastal regions or in open forest/woodland. There are none in the Red Centre.