Baulkham Hills (; colloquially known as Baulko) is a suburb in the Hills District of Greater Sydney, in the state of New South Wales, Australia. It is located within 30 kilometres north-west of the Sydney central business district mostly within the local government area of The Hills Shire, of which Baulkham Hills was formerly the administrative seat and namesake of The Hills Shire. A small section of the suburb which is located south of the Hills Motorway-Windsor Road intersection is part of the City of Parramatta.

According to the 2021 census, there were 37,415 residents in Baulkham Hills. 56.8% of residents were born in Australia. The most common countries of birth were China 8.2%, India 7.5%, England 2.3%, South Korea 2.1% and Sri Lanka 1.7%. 55.6% of residents spoke only English at home. Other languages spoken at home included Mandarin 10.2%, Cantonese 4.2%, Hindi 3.2%, Korean 2.8% and Tamil 2.1%. The most common responses for religious affiliation were No Religion, so described 29.7%, Catholic 23.4%, Anglican 10.8% and Hinduism 8.9%.

Express bus services and the new Sydney Metro North West line services the suburb.