The grant follows donations from individuals totalling more than $US8 million as a result of the Foundation's fundraising push in late 2009 and early 2010.
"We are very pleased and grateful," said Jimmy Wales, Wikipedia founder and Wikimedia Foundation board member.
"This is a wonderful gift, and we celebrate it as recognition of the long-term alignment and friendship between Google and Wikimedia. Both organisations are committed to bringing high quality information to hundreds of millions of individuals every day, and to making the Internet better for everyone," he added.
Google and Wikimedia have a history of collaboration, including work on the translation of Wikipedia content into languages such as Arabic, Hindi and Swahili.
What does Sergey Brin think of Wikipedia? Find out on page 2.
"This vast repository of community-generated content is an invaluable resource to anyone who is online," he added.