Pennant Hills is located 18 kilometres north-west of the Sydney central business district in the local government area of Hornsby Shire.

[citation needed] The first white settlement occurred in the area with the establishment of convict timber camps in the time of Governor Lachlan Macquarie.

However, the only recorded evidence of such a signalling system in the vicinity was one operating from 1824 to 1829 in the present suburb of Ermington and the use of the term 'Pennant Hills' is found in much earlier documents.

[3] In an 1801 muster list, 'Pennant Hills' is recorded as the place of residence of Ann Fay, wife of William Bellamy.

[5] In 1920 the historian James Jervis suggested that the locality had been named after the naturalist Thomas Pennant, a prominent British ornithologist and zoologist and prolific author of the eighteenth century.

Under the patronage system of the time, colonial administrators and explorers often acknowledged their English supporters by naming geographical features in their honour.

However, when the northern railway line was built it passed through what is now Pennant Hills, so a suburb grew around the station and took on the name.

[citation needed] During the 1960s and 1970s, Pennant Hills was the site of Chelmsford Private Hospital, where the unorthodox psychiatric Deep Sleep Therapy conducted by Dr Harry Bailey resulted in the deaths of dozens of patients.

[13][14][15] The Ern Holmes Oval was the home ground of the Pennant Hills Demons Australian Football Club until 2011.

Originally maintained for many years by the noted government biologist Dr Lilian Fraser, after her death in 1987 her collection of rare and exotic plants was passed on to Hornsby Shire Council.

Pennant Hills is also home to the Baden Powell Scout Centre, which borders the Lane Cove National Park.

Opened in 1929, it initially served as a permanent camp for the unemployed during the Great Depression, and was visited by the Lord Baden-Powell himself in 1931.