The last million units were sold in just nine months.

Toyota is celebrating another milestone for its hybrid lineup as cumulative sales surpass 10 million units.The milestone was reached by the end of January, just nine months after Toyota sold its nine millionth unit in late April 2016. In North America alone, Toyota sold three million hybrids and plug-in hybrids by the end of December.

"Hybrids remain an important part of our lineup of vehicles, with over 246,000 units sold last year, and we have seen continued demand with the release of the RAV4 Hybrid variant of the popular compact SUV, accounting for nearly 13 percent of its total sales volume in 2016," said Toyota's North America senior VP, Bob Carter.

The company estimates that its hybrid fleet has reduced CO2 emissions by around 77 million tons compared to traditional powertrains, while saving nearly 7.7 million gallons of gasoline.

"When we launched Prius, no one even knew what a hybrid was, but, thanks to early adopters, hybrids have ridden a wave of success into the mainstream," said Toyota co-chairman Takeshi Uchiyamada, also known as the father of the Prius.