Nielsen Park is a heritage-listed historic site, park and nature reserve located at Greycliffe Avenue, Vaucluse in the Municipality of Woollahra local government area of New South Wales, Australia. The traditional lands of the Birrabirragal indigenous people, the park was designed by John Frederick Hilly, James Barnet and the Office of the New South Wales Government Architect. It is also known as Vaucluse Estate, Greycliffe Estate and Greycliffe House. It was added to the New South Wales State Heritage Register on 28 August 2017.