The 2018 Sydney SuperNight 300 was a motor racing event for the Supercars Championship, held on the weekend of 3–4 August 2018. The event was held at Sydney Motorsport Park in Eastern Creek, New South Wales and consisted of one race, 300 kilometres in length. It was the tenth event of sixteen in the 2018 Supercars Championship and hosted Race 21 of the season.

Sydney Motorsport Park is a motorsport circuit located on Brabham Drive, Eastern Creek, New South Wales, Australia, adjacent to the Western Sydney International Dragway. It was built and is owned by the New South Wales Government and is operated by the Australian Racing Drivers Club. The circuit is one of only two permanent tracks in Australia with an FIA Grade 2 license and is licensed for both cars and motorcycles.