Barton will join the board in April and take over as chair after Rio's annual general meeting on May 5, replacing current chairman Simon Thompson.
Thompson, whose four-year stint as chairman was marred by the destruction of the Juukan Gorge caves, announced earlier this year that he would step down once a successor was found.
A Ugandan-born Canadian, Dominic spent over 30 years at McKinsey & Company, including nine as the global managing partner and six as Asia chairman.
Since 2019, he has been Canada's ambassador to China.
Prior to that, he spent one year as chairman of diversified miner Teck Resources.
Barton has previously chaired Canada's Advisory Council for Economic Growth and the International Advisory Committee to the President of South Korea on National Future and Vision.
Rio CEO Jakob Stausholm said Barton brought the skills and experience the company needed.
"I am truly looking forward to working with Dominic in our effort to continue to strengthen Rio Tinto, in particular drawing on his wealth of experience across Asia in both a business and diplomatic capacity," he said.
"I would like to thank Simon for his dedication to Rio Tinto and the support and counsel he has provided, and continues to provide, to me during a period of transformative change."
Barton described the appointment as a "great honour".
"Returning to the private sector, I am excited to join a company with world-class people and assets as it navigates a shifting competitive landscape and seeks to emerge as a leader in the climate transition," he said.
"I look forward to working with Jakob and the board to implement a strategy that puts decarbonisation at the heart of the business and positions Rio Tinto to be a leader in addressing complex global problems, while building and sustaining trust with host communities."
The global search for Thompson's replacement was jointly led by UK senior independent director Sam Laidlaw and Australian senior independent director Simon McKeon.
The process included discussions with a cross-section of the company's shareholders in relation to the attributes, experience and skills they expected in the new chair.
These included proven experience of managing highly complex, cross-border relationships with multiple stakeholders; a strong track record of working in Asia and emerging markets; a commitment to the highest ESG standards; and a proven ability to lead a board and act as a mentor to the executive team.
"The board is delighted to have appointed such an outstanding individual and I know Dominic will lead the Rio Tinto board with distinction," Laidlaw said.
"He has an impressive track-record, with extensive and broad business and diplomatic knowledge and a deep understanding of the link between business, governments and society. On behalf of the board, I welcome him to Rio Tinto."
