The Blue Mountains is a mountainous region
and a mountain range located in New South
Wales, Australia.

The region borders on Sydney's metropolitan
area, the Blue Mountains foothills starting about
50 kilometres (31 mi) west of the state capital.
The public's understanding of the extent of the
Blue Mountains is varied, as it forms only part of
an extensive mountainous area associated with
the Great Dividing Range. Officially the Blue
Mountains region is bounded by the Nepean
and Hawkesbury rivers in the east, the Coxs
River and Lake Burragorang to the west and
south, and the Wolgan and Colo rivers to the
north. Geologically, it is situated in the central
parts of the Sydney Basin.

The Blue Mountains area includes the local
government areas of the City of Blue
Mountains, the City of Hawkesbury, the City of
Lithgow and Oberon Shire.