The photographic studio Johnstone, O'Shannessy & Co was established in Melbourne, Australia, in 1865 when Henry James Johnstone of Johnstone & Co went into partnership with Emily O'Shannessy and George Hasler.

The company was the leading photographic portrait studio in Melbourne, providing services to governors, visiting royalty, politicians and other prominent members of society.

Henry James Johnstone left the firm in 1876, but the company continued to expand without him, under the management of George Hasler. On Hasler's death in 1897, his son-in-law Rupert De Clare Wilks took over the company, but an economic downturn in the first decade of the 20th century saw the company go into liquidation in 1905.