Kellyville is a suburb of Sydney, in the state of New South Wales, Australia 36 kilometres north-west of the Sydney central business district in the local government area of The Hills Shire. It is part of the Hills District region.

In the 2016 census, the population of Kellyville was 27,971. Residents had a younger median age than the country overall: the median age was 35 years, compared to the national median of 38 years. Children aged under 15 years made up 24.3% of the population (national average is 18.7%) and people aged 65 years and over made up 8.9% of the population (national average is 15.7%). 61.0% of residents were born in Australia, the next most common countries of birth were India 4.2%, China 4.1%, England 3.0%, South Africa 2.2% and Philippines 2.0%. 64.3% of residents only spoke English at home. Other languages spoken at home included Mandarin 5.3%, Cantonese 2.5%, Hindi 2.3%, Arabic 2.0% and Persian 1.6%.

Windsor Road is a significant road linking Parramatta, in the City of Parramatta, with Windsor, in the City of Hawkesbury. Recent infrastructure development in the Hills District has increased the accessibility of Kellyville. Windsor Road, formerly one-lane each way, was upgraded to a two-lane road in 2006 and has significantly improved traffic flow in the area. Green Road was completed as a two-lane road in 2006 and links Kellyville with the nearby Victoria Avenue, Castle Hill trading zone 2 km down the road, home to three Homemaker centres, car dealers, light industrial areas and many other retail outlets. The old Glenhaven Bridge is a wooden, shared one-lane bridge and was replaced with the new Glenhaven Bridge, which is a proper concrete bridge suitable for heavy vehicles. Built in 2007, the bridge runs over Cattai Creek and allows for normal traffic flows between Kellyville and Glenhaven. An unorthodox bailey bridge (Circa ?) and former roadway have been retained in Golden Grove Reserve. This former road bridge can be found between James Mileham Dr and Geewan Ave in the reserve. This bridge once was the extension to Acres Road joining Hezlett Road.