The doodle features an illustration of five generic sports people - a footballer, swimmer, runner, javelin thrower and fencer - integrated with the letters that spell Google.
Google doodles are a way for the world's most popular search engine to mark the major events and landmarks making the news around the planet.
The site has previously adapted its homepage logo to celebrate various historical figures, including aviator Amelia Earhart, inventor Thomas Edison and music legend John Lennon, along with key anniversaries such as the 30th anniversary of the ZX Spectrum.
It has also played host to an interactive Pac-Man game, music making doodle and a video of pumpkin carving for Halloween.
Clicking on the London 2012 doodle takes users through to Google's London 2012 Olympic Games search page, featuring the latest news stories, related searches and additional content.
London 2012 is not the first Olympics to get the Google treatment, however, as the homepage was also adapted for the 2008 Summer Olympics in Beijing, China.
As with the Beijing Games, the London Olympics is also expected to get further Google doodles throughout the Games and Paralympic Games, including specific designs for each major sport.
Picture gallery - London 2012:
Copyright: Martin Rickett/PA Wire/Press Association Images