Thornleigh is a residential suburb located approximately 22 kilometres north-west of Sydney's central business district, within the Hornsby Shire local government area. Hilly terrain, leafy streets, and proximity to natural bushland reserves characterise the suburb.
As of the 2016 Census, Thornleigh had a population of 8,898 residents. The demographic profile indicates that 61.8% of the population was born in Australia, with significant communities originating from China (6.4%), India (3.7%), England (3.5%), South Korea (2.1%), and the Philippines (1.9%). Languages spoken at home include English (66.0%), Mandarin (7.2%), Cantonese (3.5%), Korean (2.9%), Arabic (2.7%), and Hindi (1.6%). The median age was 40 years, slightly above the national median of 38 years.
Public transportation in Thornleigh is facilitated by the Thornleigh railway station on the Northern Line of the Sydney Trains network, providing access to the Sydney CBD and other areas. Bus services operated by CDC NSW connect the suburb to neighbouring regions, including Hornsby, Westleigh, Normanhurst, and the Sydney Adventist Hospital.
Essential establishments in the suburb include the Thornleigh Marketplace shopping centre, which features a Woolworths supermarket and a variety of specialty stores. The area also hosts several churches, including St. George Maronite Catholic Church and Thornleigh Community Baptist Church. McDonald's Australian headquarters and a Bunnings Warehouse operate in Thornleigh.
Recreational activities are supported by various parks and facilities. The Thornleigh Sports and Recreation Club offers divisions in baseball, basketball, cricket, netball, soccer, and softball. The Brickpit Park features a skate park, basketball courts, and the Thornleigh Golf Centre, which includes driving ranges and mini-golf courses.
The housing landscape in Thornleigh predominantly consists of separate houses, with some areas featuring early examples of Federation and Californian Bungalow style properties. The suburb's blend of residential character, accessibility, and proximity to natural reserves contributes to its appeal as a family-friendly locale.