- "To be honest, I'm never entirely sure which I prefer: the study or the outdoors. Both offer opportunity to expand the mind. One offers safety to the body, the other to the soul. I suppose I have been lucky to enjoy both in equal measure."
- ―William de Saint-Prix.[src]
William de Saint-Prix was an Assassin born to a wealthy family of French descent. Receiving the best education, he was particularly adept at science and literature, and had gained the knowledge to design both his own weapons and fighting style.
On his 17th birthday, William was sent to America, where he was to fight for the cause. As his actions against the Templars earned him the admiration of his fellow American members, he lived in the outskirts of Boston ever since. Though he was shunned by the revolutionaries for his noble beginnings, his intelligence and courage earned him the respect of his Assassin compatriots.
In 2012 and 2013, his genetic memories were used as an Animi Avatar by the entertainment branch of the Templar company Abstergo Industries, to influence the general public via the Animus games console, under the title of the Huntsman.
- William shares the same surname as Nicolas de Saint-Prix, another French Assassin, though the relation between the two is unknown.
- An Assassin with similar clothing to Saint-Prix is present with Connor in the Assassin's Creed 3 target render gameplay.