Hornsby is a suburb on the Upper North Shore of Sydney in the Australian state of New South Wales north-west of the Sydney central business district. It is the administrative centre of the local government area of Hornsby Shire.
The name Hornsby is derived from convict-turned-constable Samuel Henry Horne, who took part in the apprehension of bushrangers Dalton and MacNamara on 22 June 1830. In return he was granted land which he named Hornsby Place.
The first European settler in the area was Thomas Higgins, who received a grant of land in Old Mans Valley. A railway station named "Hornsby Junction" opened on 17 September 1886 to the north of the town of Hornsby, which had developed on the site of Horne's grant. It formed the junction of the Northern Line and the North Shore Line which were yet to be completed at that time. Hornsby station was one stop further south on the Northern Line. Due to confusion by commuters alighting at the incorrect station expecting to transfer to a connecting train, the old Hornsby station was renamed Normanhurst on 17 November 1898 after prominent local activist and engineer Norman Selfe, while the Hornsby Junction station assumed the current name of Hornsby.
The first Hornsby Post Office opened on 1 August 1864, and was renamed South Hornsby on 1 May 1900, the same day Hornsby Junction office near the railway station (open since 1887) was renamed Hornsby. The latter office remains open; the South Hornsby office was renamed Normanhurst in 1905.
The Hornsby Shire Council was established in 1906. In 1961, The Westfield Group built a shopping mall at Hornsby, making it one of the first suburbs in Sydney with a modern-style shopping centre. A competing shopping centre, Northgate, opened in 1979 but was eventually bought by Westfield. In late 1999, the two sites were amalgamated when the original Westfield was demolished and Northgate was renovated to create the new Westfield Hornsby which opened in November 2001.