William Cooper (18 December 1860 or 1861 – 29 March 1941) was an Aboriginal Australian political activist and community leader; the first to lead a national movement recognised by the Australian Government.

William Cooper was born in Yorta Yorta territory around the intersection of the Murray and Goulburn Rivers in Victoria, Australia on 18 December 1860 or 1861. His family was a small remnant of what Cooper recalled as a large tribal group, "As a lad I can remember 500 men of my tribe, the Moiras, gathered on one occasion. Now my family is the only relic of the tribe." From there Cooper appears to have been forced by necessity to work for a variety of pastoral employers, even as a child.

On 4 August 1874, William Cooper, along with his mother, Kitty, his brother Bobby and other relatives arrived at Maloga, an Aboriginal mission on the Murray, run by Daniel and Janet Matthews. Three days later, Matthews was struck by William's quick progress in literacy, and noted the following in his diary:

6 Aug. Maloga. The boy, Billy Cooper, shows great aptitude for learning. He has acquired a knowledge of the Alphabet, capital and small letters, in three days and then taught Bobby – capitals only – in one day.

From there, Cooper's education on the mission was sporadic; there was no requirement for Cooper to attend any school, and he moved to and from the mission freely. In an interview Cooper gave when he was 76, he said he had just seven months' regular schooling.

Instead of school, Cooper said he spent much of his childhood into his teens working in the household of Sir John O'Shanassy, a pastoralist, Victorian Member of Parliament and one-time Premier of Victoria who owned several stations, including the Moira run (on Cooper's own mother's country). Through these pastoral networks, he travelled much of Australia as a teenager, even seeing "the remains of the Burke and Wills Expedition at Cooper’s Creek" in the remote Lake Eyre Basin.

However, Cooper kept a connection with the missionary Daniel Matthews and, in his 20s, he returned to Maloga, which appears to represent very happy years. In a letter he wrote towards the end of his life to the missionary's youngest daughter, Alma, he recalled Daniel and Janet and the Maloga community in very warm terms:

I often cast my mind back to them, and the dear old place, and at times it brings tears in my eyes when thinking of the glorious hours, days and months, we spent together; the beautiful singing, the picnics, the games. — Your father’s voice still rings in my ears: We never ever had singing like we did at Maloga.