The ban was legislated by the South Australian parliament in September last year.
People found to be breaching the laws banning the sale, supply and distribution of single-use items face fines ranging from $315 to $20,000.
The ban comes as Victoria announced it will phase out single-use plastics by 2023.
Queensland has also introduced legislation to ban straws, plastic cutlery and plates from July 2021.
It is a movement that has gained traction around the world.
China, the world's biggest importer of plastic, has banned single-use bags and straws.
The European Union, with nearly half a billion people, has also banned single-use plastic cutlery, plates, cotton buds and polystyrene containers.
