The total, global internet audience hit the 1 billion mark in December 2008, according to stats from comScore's World Metrix audience measurement service.
Breaking down the audience into regions, the Asia-Pacific region has the highest share of internet users at 41%, followed by Europe at 28% and North America at 18%.
"Surpassing one billion global users is a significant landmark in the history of the internet", said Magid Abraham, president and chief executive officer, comScore.
"It is a monument to the increasingly unified global community in which we live and reminds us that the world truly is becoming more flat. The second billion will be online before we know it, and the third billion will arrive even faster than that, until we have a truly global network of interconnected people and ideas that transcend borders and cultural boundaries".
As far as countries go, comScore says China has the biggest audience at 179,710,000 or 17.8% of the total worldwide audience, the US comes in at 163,300,000 and the UK at 36,664,000 or 3.6%.