Barra, 51, is currently executive vice president for global product development, purchasing and supply chain. She was elected CEO by the GM board, which she will join. She has worked at GM for 33 years.
Akerson is 65. GM said he moved his succession plan ahead by several months after his wife was recently diagnosed with an advanced stage of cancer. He will step down as CEO and chairman on Jan. 15, 2014.
"My goals as CEO were to put the customer at the center of every decision we make, to position GM for long-term success and to make GM a company that America can be proud of again," Akerson said in a prepared statement. "We are well down that path, and I'm certain that our new team will keep us moving in that direction."
The board named Tim Solso, 66, to succeed Akerson as chairman. Solso is the former chairman and CEO of Cummins, and has been a GM board member since June 2012.
Barra has been a leader in the ongoing product development process that has been among the underpinnings of GM's turnaround.
"With an amazing portfolio of cars and trucks and the strongest financial performance in our recent history, this is an exciting time at today's GM," she said in a prepared statement.
In other changes, Dan Ammann, 41, executive vice president and chief financial officer, was named president. He will retain CFO responsibilities at least through the release of the company's fourth-quarter and full-year 2013 results in early February 2014. His replacement as financial chief will be named later.