The Android storefront, which hosts more than 675,000 apps and games, will hold a sale on selected products for the next five days to celebrate the achievement.
Apps from leading developers including Gameloft, Electronic Arts, Rovio, runtastic, Full Fat and more will be available at a slashed price, as well as special collections like 25 movies you must own, 25 banned books and 25 albums that changed the world.
"25 billion is more than twice the distance, in miles, than the Voyager 1 spacecraft has travelled since its launch 35 years ago," said Google's director of digital content Jamie Rosenberg.
"It's the amount of time, in minutes, that have passed since some of our earliest ancestors began to set foot in Europe. And now, thanks to all of you, it's a Google Play milestone. We look forward to the next 25 billion."
Google Play was launched in March this year when the company rebranded its digital distribution service and merged the Android Market and Google Music.