Castle Hill is an electoral district of the Legislative Assembly in the Australian state of New South Wales.

It is a conservative urban electorate in the Hills District in Sydney's north west.

It was first contested at the 2007 election, when it was won by Michael Richardson, previously the member for The Hills.

In the first three elections after its creation, Labor was lucky to win 30 percent of the two-party vote.

After the 2015 election, it was the safest seat in the state, with a 29.4 percent swing needed for Labor to win it.