Arcadia is a semi-rural suburb of Sydney, in the state of New South Wales, Australia 42 kilometres north-west of the Sydney central business district in the local government area of Hornsby Shire.

According to the 2021 census of Population, there were 1,475 residents in Arcadia. 79.6% of residents were born in Australia. The most common other countries of birth were England (4.8%), New Zealand (2.0%), South Africa (1.0%), Scotland (0.9%) and China (0.9%). 88.1% of residents spoke only English at home. Other languages spoken at home included Italian (1.3%), Arabic (0.9%), Mandarin (0.9%), German (0.5%) and Croatian (0.4%). The most common responses for religious affiliation were No Religion, so described (33.3%), Catholic (27.0%) and Anglican (17.5%).

Arcadia Road is the main road through the suburb that provides access from Galston and leads north into Bay Road to Berrilee and Berowra Waters. Arcadia Road also links to Cobah Road which leads north to Fiddletown.