Electoral district of Hornsby is an electoral district of the New South Wales Legislative Assembly in Australia.

Hornsby is one of two post-1927 electorates to have never been held by the Labor Party, and always by the Liberal Party, a predecessor party to the Liberals, or an independent, the other being Vaucluse.

[a] The seat is currently represented by James Wallace of the Liberal Party, following the by-election held on 19 October 2024, after Matt Kean's resignation.

On its current boundaries, Hornsby takes in the suburbs of Asquith, Berrilee, Berowra, Berowra Heights, Berowra Waters, Brooklyn, Canoelands, Cowan, Dangar Island, Galston, Glenorie, Hornsby Heights, Laughtondale, Mount Colah, Mount Kuring-gai, Singletons Mill, Sunny Corner and parts of Dural, Hornsby, Middle Dural, Pennant Hills, Round Corner, Thompsons Corner and Wisemans Ferry.