Willoughby is a suburb located on the lower North Shore of Sydney, in the state of New South Wales, Australia 8 kilometres north of the Sydney central business district, in the local government area of the City of Willoughby.

Captain Arthur Phillip's search for "good land, well watered" led to the discovery and colonisation of the rough shores of Roseville Chase, where Samuel Bates built a farm at Echo Point.

In 1934, the Willoughby incinerator was built in Small Street, after a design by Walter Burley Griffin.

The suburb was home to the headquarters of the Nine Network, under the callsign of TCN-9 for 64 years until it moved to North Sydney in November 2020.

Next to this site was the Channel 9 TV Tower which at 233 metres high was the tallest in Australia; its demolition commenced in April 2021,[4] to be replaced by 460 new homes.

Flat Rock Gully, built on an old rubbish tip, is bushland with two walking tracks to Long Bay, following the creek line.

The next most common countries of birth were China (without SARs and Taiwan) 4.6%, England 4.4%, Hong Kong 2.5%, New Zealand 2.0% and South Africa 1.3%.