Announcing the achievement on its blog, Google said the store was currently growing at a rate of one billion downloads per month.
It is marking the occasion by running a 10-day promotion offering selected apps for only 10 pence each in the UK and 10 cents in the US.
In October Apple revealed it had notched up 18 billion app downloads, 10 months after passing the 10 billion figure, since launching its app store in 2008.
In the UK market, Android overtook Apple in the spring to become the most used smartphone platform.
However, some industry observers have been critical of the overall quality of Android apps in comparison to those available on Apple’s iOS platform.
Google charts the rise of Android on its blog