General Motors Co
The Detroit-based automaker's return to the top slot comes as Japanese rival and former No. 1 seller Toyota Motor Corp <7203.T> slips in the rankings after an earthquake in Japan and deadly floods in Thailand hampered its production in 2011.
GM said it sold 9.026 million vehicles globally last year, up 7.6 percent from 2010.
Toyota will publish its final sales results for 2011 later this month but has projected sales of 7.9 million in 2011, down about 6 percent from a year earlier.
The tabulation of global auto sales is not without controversy. Rankings are mostly about bragging rights, but there has been a long-running and robust debate over how to account for vehicles sold through affiliates.
The sales figures released by GM, which was the largest automaker until 2008 when Toyota took its place, include vehicles sold through its joint ventures in China. Some analysts extract those sales from GM's results.
Depending on how the results are tallied, Toyota may have finished the year in third place. However, Toyota would fall to fourth place behind Renault SA
Including AvtoVAZ, Renault-Nissan sold 8.03 million cars worldwide last year. This includes the 638,000 cars sold by AvtoVAZ, in which Renault owns a minority 25 percent.
The International Organization of Motor Vehicle Manufacturers, a global trade group based in France, has not yet released its annual ranking of automakers by production.
TOYOTA MOUNTS COMEBACK
Toyota's 2011 worldwide sales tally included listed subsidiaries Daihatsu Motors Co <7262.T> and Hino Motors Ltd <7205.T>.
Toyota's sales were hurt by a series of disasters that triggered auto parts shortages and curtailed its vehicle production last year.
But now Toyota is ramping up production to rebuild depleted inventory and will add output capacity in emerging markets such as Brazil and China this year. However, analysts said it also faced stiffer competition as rivals step up their game.
Toyota's biggest problem is that even without the natural disasters, its sales weren't exactly growing, JP Morgan auto analyst Kohei Takahashi said.
The ranking is not that important, but they need a convincing strategy to boost their sales, he said, adding that Toyota was behind rivals such as Nissan in rolling out small cars for emerging markets.
Toyota has lagged the sharper sales growth at rivals such as Nissan and Hyundai Motor Co <005380.KS> because of a relatively slow push into emerging markets as it scrambled to meet runaway demand in mature markets in the past decade.
In a bid to catch up, Toyota is adding factories in Brazil, China, Thailand and elsewhere, aiming to sell half its cars in emerging markets by 2015, up from around 40 percent now.
South Korean sister carmakers Hyundai Motor Co <005380.KS> and its 34 percent owned Kia Motors Corp <000270.KS> racked up total sales of 6.53 million last year.
(Reporting by Deepa Seetharaman in Detroit, Chang-Ran Kim in Tokyo; Editing by Mark Bendeich)