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:

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.

Forum discussion at WebmasterWorld and Google Blogoscoped Forums.