Prime Minister Stephen Harper announced the appointment Thursday, praising Dowdeswell's "wealth of expertise" and her work promoting sustainable development in Ontario and across the country.
"She has been a senior public servant, worked in government, worked in international organizations and non-governmental organizations, business and also most recently, academically focused organizations," Harper said as he introduced the new lieutenant-governor.
"So she brings a lot of public-service experience to the job, and we're delighted that, Liz, that you've accepted to do this on behalf of the Crown, on behalf of the people of Ontario."
Dowdeswell replaces David Onley, who held the position for seven years.
"Ms. Dowdeswell's focus has been on engaging the general population on public policy-making and seeking innovation in the successful management of organizations through change," according to a biography on the lieutenant-governor's website.
Ontario Premier Kathleen Wynne released a statement welcoming the lieutenant-governor-designate, who will be sworn in at a later date.
"Elizabeth Dowdeswell's remarkable career and accomplishments make her eminently worthy of this honour," Wynne wrote. "Dowdeswell has contributed extensively to public and environmental policy. She has impressive experience on the national and international stage. Among her numerous executive leadership roles, she was the executive director of the United Nations Environment Program, the first woman to hold that position."
She is currently the president and CEO of the Council of Canadian Academies. Prior to that was the founding president and CEO of the Nuclear Waste Management Organization and has held various United Nations positions.
Dowdeswell has been actively involved in community service aimed at promoting a "healthy environment, sustainable energy and development and a better quality of education both at home and abroad," the prime minister's office said in a statement.
She served as a deputy minister of culture and youth in Saskatchewan and was later assistant deputy minister at Environment Canada.
Dowdeswell was appointed as an officer of the Order of Canada in 2012 and received a Queen's Diamond Jubilee Medal in the same year.
She serves on a number of boards, including as the chairwoman of the board of directors of the Higher Education Quality Council of Ontario. Dowdeswell has a teaching certificate and a bachelor of science degree in home economics from the University of Saskatchewan and a master of science degree in behavioural sciences from Utah State University.
Ontario NDP Leader Andrea Horwath issued a statement congratulating Dowdeswell on the appointment.
"I know she will uphold the office with integrity," Horwath wrote. "Ms. Dowdeswell has an impressive track of public service across Canada and abroad."