Thomas Chirnside (1815–1887) was an Australian pastoralist who developed much of what would become western Melbourne.
Thomas Chirnside was born in Berwickshire, Scotland, the elder son of Robert Chirnside and Mary Fairs. His father was also a farmer.
In 1839 Chirnside came from Liverpool in the Bardaster. He arrived in Adelaide in January and Sydney in March of that year. The drought of 1839 affected the sheep he had left on the Murrumbidgee, so he joined his brother in Melbourne.
In April 1842 the brothers established a station in the Grampians, and Thomas employed Aborigines on another station in the area. Throughout 1843 they built developments in the Western District.
The elder Chirnside settled in Werribee just before the gold rushes, eventually buying 80,000 acres (320 km²) of land. He built a sandstone mansion which is now the Werribee Park Mansion.
On 2 September 1853 he purchased through a government grant Section 14, Parish of Cut Paw Paw, County of Burke. This allotment was 89 acres (360,000 m2), and is now the new town of Kingsville.
Thomas Chirnside was a member of the Philosophical Institute of Victoria from 1857 to 1859 and the Royal Society of Victoria from 1860 to 1866.
In 1874 the elder Chirnside sold land to his brother Andrew. From 1874 to 1877 the elder Chirnside built Werribee Park Mansion.
Thomas Chirnside committed suicide in 1887. He was found dead in the laundry at Werribee Park with a shotgun lying beside him. Andrew Chirnside then passed on the land.