Apple saw the iPhone’s market share triple over the past year, capturing 12.9 percent of the worldwide smartphone market, according to a new Gartner analysis. This is a huge number in this market.

For the quarter ending September 30 2007, iPhones accounted for 3.4 percent of the market. That figure was more than 3x higher on the same day in 2008.

Nokia is the leader worldwide in smartphone sales, with 42.4 percent of the market. BlackBerry maker Research in Motion comes in third with 15.9 percent. In North America, Apple is in second place behind RIM, with iPhones accounting for over a quarter of all smartphones sold across the US.

Gartner analysts also noted that this quarter marked the first time iPhone sales exceeded those of Windows Mobile devices; that’s pretty astonishing when you consider how many flavors of WM handsets are out there, and how much of a headstart they had in the marketplace.

Some reports suggest the iPhone could again double its market share in the next year or so.