Square Inc. has announced today that world-renowned entrepreneur and philanthropist Sir Richard Branson, an English business magnate, best known for his Virgin Group of more than 400 companies has become one of its investors. The company recently closed a $100M Series-C financing round led by Kleiner Perkins Caufield and Byers.

Branson, known for his success building hundreds of companies around the world, took interest in Square’s rapid growth and novel technology, in particular its free hardware that allows anyone to accept credit card payments anywhere,

“I’m very passionate about helping people start and grow successful businesses, and Square is an incredible technology that inspires and empowers everyone to be an entrepreneur,” said Sir Richard Branson.

Square enables anyone to accept credit cards anywhere. Square offers an easy to use, free credit card reader that plugs into a phone or iPad. It’s simple to sign up. There is no extra equipment, complicated contracts, monthly fees or merchant account required.

Square has shipped over 800,000 card readers to merchants and is currently processing over $2 billion in payments annually. While currently focused on its U.S. growth, the company plans to offer Square in international markets in 2012.