The company said on Tuesday that Akerson, who is also the chairman, will leave on January 15, moving forward his planned departure by at least six months. He said he had planned to leave in mid- to late-2014, but accelerated his exit after learning about two months ago that his wife had an advanced stage of cancer.
Barra will be GM's fifth CEO in less than five years since Rick Wagoner was forced out by the Obama administration in March 2009.
Barra, 51, GM's executive vice president for global product development, purchasing and supply chain, was elected by the board as the next CEO and will be the company's fifth female director on the current board. Theodore Solso, 66, will succeed Akerson, 65, as chairman.
Akerson cited Barra's breadth and depth of experience, her managerial and interpersonal skills, and understanding of the company. He also said she had "brought order to chaos" in the global product development process.
"This is an executive who has a vision of where she wants to take the organization," he said on a conference call. "Mary is an adaptive personality and one who reacts to change well."
Under Akerson, GM had moved to eliminate some of its historic bureaucracy and inefficiencies, recovered its investment grade credit rating, and pared financial losses in its European business.
However, Akerson said Barra and her reshuffled executive team will need to finish the job, including completing the reduction of the number of platforms on which it builds cars and trucks globally, and strengthening overseas operations.
"The bankruptcy transformed the balance sheet, but the transformation of the company is still a work in progress," Guggenheim Securities analyst Mathew Stover said. He added that only time will tell whether Barra, who has spent her entire career at GM, is the change agent as touted by Akerson.
Barra's ascension also marks the re-emergence of an engineer as the next leader at GM, a company long dominated by financial executives.
"The promotion of Barra as CEO indicates there is more to come in the evolution of the company and may attract some new longer-term investors who were skeptical about an over finance-dominated executive suite," Barclays analyst Brian Johnson said in a research note.
As Akerson leaves the helm at GM, Ford Motor Co (F.N) is also on the verge of a possible change at the top. Ford CEO Alan Mulally is on a short list to become the next CEO at Microsoft Corp (MSFT.O).
CHOOSING A SUCCESSOR
The news comes a day after the U.S. Treasury announced it had sold the last of its GM shares, which could clear the way for the restoration of a common stock dividend, a move investors have been hoping for.
Sources told Reuters last month that Akerson might step down in 2014, a move widely expected once the government exited its stake. He was appointed CEO just before GM re-entered public markets on November 2010, following a $49.5 billion government bailout and bankruptcy reorganization.
Speculation on his exit gained steam in April, when GM disclosed in a securities filing that his compensation plan had changed. The CEO did not receive any restricted stock units last year "in acknowledgement of the possibility of his retirement before the completion of the three-year vesting period," which would be in 2015.
Some GM employees and analysts said Akerson gave Barra's candidacy a boost in September when he said it was "inevitable" that a woman would one day run one of the U.S. automakers. In addition to the women on the board, GM has several female executives in senior management.
Akerson said on Tuesday that the board did not look outside the company for his successor and Barra's selection was unanimous.
He said Barra was chosen for her talent, not gender. He also said it was the board's decision to split the chairman and CEO jobs, a move he supported.
In 2013, women accounted for 4 percent of CEOs in Fortune 500 companies and only 3.3 percent of those at durable goods manufacturers, according to advocacy group Catalyst.org.
With 33 years of experience at GM, Barra has risen through a series of manufacturing, engineering and senior staff positions, and is currently in charge of reducing the number of platforms on which GM builds its vehicles. Her father worked as a die maker at GM for 39 years.
"The key to General Motors' long-term success is great products," Barra said in a video posted on the company's website on Tuesday.
Independent auto analyst Maryann Keller said Akerson's successor will be his biggest legacy, and Barra has many of the attributes that Mulally used to help turn around Ford after his arrival in 2006.
"Akerson's tenure is too short and will be measured on whether or not he has chosen the best successor," she said. "She is an excellent choice, but you won't know that until she actually starts the job and appoints the people she wants to help her finish a job that is only partly done."
OTHER EXEC CHANGES
In other management changes, GM said Chief Financial Officer Dan Ammann, 41, would assume the title of president, while North American chief Mark Reuss, 50, would replace Barra as head of product development. Alan Batey, currently vice president of global Chevrolet, will replace Reuss as head of North America.
Ammann will assume responsibility for managing the company's regional operations around the world as well as having the Chevrolet and Cadillac brand operations and GM Financial report to him. Analysts welcomed his promotion as it keeps the highly regarded executive in the fold and gives him the operational experience many felt he lacked to round out his resume.
Akerson said with Treasury's exit as a shareholder, GM's executive compensation will become more performance-oriented with as much as a quarter tied to quality.
GM did not name a replacement for Ammann as CFO. Ammann will retain his CFO duties through the release of fourth-quarter results in February.
Vice Chairman Steve Girsky, 51, will move to a senior adviser role until leaving the company in April, GM said. He will remain on the board.
Solso is the former chairman and CEO of Cummins Inc and has been a member of the GM board since June 2012. Guggenheim's Stover expects Solso to be an active chairman at GM.
Shares of GM were down 0.9 percent at $40.55 on Tuesday afternoon on the New York Stock Exchange.