The house flag of the Adelaide Steamship Co. Ltd, Adelaide. On a white field, there is a blue cross with a red, eight-pointed star in the centre. The design was based on the 'X' flag from the signal code. The flag is made of a wool and synthetic fibre bunting. It has a cotton hoist and is machine sewn. A rope is attached.

The company was founded in Adelaide on 9 October 1875 to run Adelaide-Melbourne services; these began operation in December 1876. It took over the Spencer's Gulf Steam Ship Co. in 1882. Services were extended to Sydney in 1887 and to Queensland in 1893. In 1915 the fleet of Coast Steamships, and the Adelaide Steam Tug Company Ltd were purchased.

A new company of the same name was incorporated on 3 February 1920 (the second time the company had been liquidated and reconstructed in the interests of more profitable operation). During the 1940s in the face of a decline in trade, the company began to diversify. It merged its fleet with that of McIlwraith McEacharn Ltd in a new company, Associated Steamships Ltd, in 1964. The company's connection with ship owning and operating ceased in 1977.