"It has become clear to me that to unify the organization it would be better for me to withdraw and pave the way for change," Parkin said in a written statement.
Parkin's career at Adidas spanned 23 years, according to Adidas AG Supervisory Board Chairman Igor Landau, who said Parkin "has always acted in the best interest of our company and our people."
"His decision to leave the company reflects that commitment and his belief that a new HR leader will better drive the pace of change that Adidas needs at the moment," Landau said in a written statement.
Leaving Tuesday, Parkin said she is committed to the company's goals of being more "diverse, inclusive, and equitable."
Adidas said CEO Kasper Rorsted will take over as acting head of Human Resources until a more permanent replacement is found.
Rorsted recently sponsored a Global Committee to Accelerate Inclusion and Equality for Adidas, which the company says includes internal decision makers "from different racial and ethnic backgrounds" around the world.