The Gulidjan, also known as the Colac tribe, Colijan, Colagdians, Kolakgnat, are an indigenous Australian tribe whose traditional lands cover the Lake Colac region of Victoria, Australia. They occupied the grasslands, woodlands, volcanic plains and lakes region east of Lake Corangamite, west of the Barwon River and north of the Otway Ranges. Their territory bordered the Wada wurrung to the north, Djargurd Wurrung to the west, Girai Wurrung to the south-west, and Gadubanud to the south-east.
The Gulidjan, like other Victorian tribes, lived for tens of thousands of years carrying out a semi-nomadic subsistence lifestyle with a system of lore and spirituality interwoven with a sense of place and their role in the geographical landscape.
The Gulidjan people were hit hard by the European invasion and settlement with most of their lands occupied by squatters by 1838, just 3 years after the Foundation of Melbourne. The Gulidjan actively resisted settlement by driving off livestock and raiding stations. Such raids inevitably brought retribution by parties of settlers with violent clashes ensuing. Ian Clark reports on three documented attacks in 1839-1840 resulting in Aboriginal deaths. More often squatters destroyed campsites and took implements as revenge.
The deaths of Joseph Gellibrand and George Hesse in 1837 - their fate remains a mystery to this day - were blamed on the Gulidjan with retribution delivered by a settler party accompanied by several Wada wurrung people killing several Gulidjan people.
In September 1837 Gulidjan numbers were estimated at between 35 and 40, with their numbers staying relatively stable into the 1850s where their population was estimated at 78 (43 males and 35 females). With the influx of people searching for gold in the Victorian gold rush during the early 1850s, by 1857 only 16 Gulidjan survived according to Aldo Massola. Causes of this decline were identified in 1862 as starvation due to European occupation of the best grassed areas of their lands; European diseases such as chicken pox, measles and influenza; association with convicts; and tribal enmity.