The 1 billion club is a rarefied field, composing such superstars as Facebook and YouTube.
Now that space is a bit more crowded with the inclusion of Gmail.
The news came amidst Google's recent earning report, which revealed Gmail now has over 1 billion monthly users. In 2012 Gmail had just 425 million monthly users, and 900 million last May.
It also brings Gmail into the same league as other Google heavyweights including Search, Maps, Chrome and Google Play.
According to recent figures, some 75% of customers access Gmail from a mobile device. The news comes as Google increases its offering for marketers and mobile users.
Google Drive has recently been beefed up for mobile, while Inbox by Gmail composes automatic replies for you.
2016 has started off well for Google. It's recently formed parent company Alphabet just leapfrogged Apple to become the most valuable public company in the world.