The Wall Street Journal broke the news based off of comScore data that Google reached over one billion visitors for the month of May.
This is a huge number, a number Facebook was expected to reach first but did not.
As the WSJ explained:
Over the past year, Google’s unique visitors per month have increased 8.4% to just over one billion. During the same period, Microsoft maintained the No. 2 position with 905 million unique visitors in May, up around 15%, while Facebook’s count surged by 30% to about 714 million visitors. In May, Yahoo saw 689 million visitors, up 10.8% over the past year, though it was surpassed by Facebook in October.
This includes all Google sites, including Google.com, YouTube.com, Gmail, Orkut and all their properties.
Here is a chart posted by Search Engine Land.
That is a lot of traffic, but in terms of time spent on the site, Facebook beats.