Demonstrations have taken place in Sydney, with smaller protests held in Melbourne and in Brisbane at the Botanic Gardens, against tight restrictions imposed to tackle a rise in Covid cases.
People chanted "freedom" as they marched through the centre of Sydney.
Officers say they have made 57 arrests.
A statement from the force says, "the NSW Police Force recognises and supports the rights of individuals and groups to exercise their rights of free speech and peaceful assembly, however, the protest is in breach of the current Covid-19 Public Health Orders."