Cumberland County is a county in the State of New South Wales, Australia. Most of the Sydney metropolitan area is located within the County of Cumberland. The County of Cumberland stretches from Broken Bay to the north, the Hawkesbury River to the north-west, the Nepean River to the west, the Cataract River to the south-west and the northern suburbs of Wollongong to the south.

New South Wales, like most (if not all) other Australian states, is divided up into nearly two hundred counties, for the purposes of surveying and the registration of land titles. Few Australian counties have ever had any government or administrative function. However, the County of Cumberland did have a county government, the Cumberland County Council, from 1945 to 1964. Its responsibilities were primarily limited to town planning on the metropolitan scale. The Cumberland County Council was not elected by the people, but rather was elected by councillors of the various local governments within the County. In 1951 the Council ratified the Cumberland County Council Planning Scheme which boldly reformed town planning throughout metropolitan Sydney. Though not all of the plan was implemented, much of it was, radically altering the urban form of Sydney and its suburbs.

The objectives of the County Council were often in conflict with the aims of many State Government departments. For instance, the County Council's plans called for a green belt to encircle metropolitan Sydney, while the NSW Housing Commission wished to use much of this land to build new low-density public housing estates in areas such as Blacktown and Liverpool. As a result, the Cumberland County Council was dissolved in 1964.

Its metropolitan planning functions were taken over by a new body, the State Planning Authority, which has since been superseded by a succession of state government departments. As of 2006 this government department is the New South Wales Department of Planning.

Sydney | Geography of New South Wales