The 20-year-old joins the Eredivisie club having spent four years as part of United's youth set-up.
He was a regular for our Under-21s last term and this move represents a great opportunity for Bjorn to gain senior experience in a new environment.
Hardley also returns to the country of his birth and will initially play for FC Jong Utrecht, FC Utrecht's youth side.
The defender arrived at Old Trafford in 2019, after beginning his career in the NAC Breda youth system.
Last season, he played in the EFL Trophy and Premier League 2 for our Under-21s, accumulating 27 appearances and one goal.