The Chief Secretary's Building is a heritage-listed state government administrative building of the Victorian Free Classical architectural style located at 121 Macquarie Street, 65 Bridge Street, and at 44–50 Phillip Street in the Sydney central business district of New South Wales, Australia. The ornate five-storey public building was designed by Colonial Architect James Barnet and built in two stages, the first stages being levels one to four completed between 1873 and 1881, with Walter Liberty Vernon completing the second stage between 1894 and 1896 when the mansard at level five and the dome were added.

Australian non-residential architectural styles are a set of Australian architectural styles that apply to buildings used for purposes other than residence and have been around only since the first colonial government buildings of early European settlement of Australia in 1788.