"This year's RBS 6 Nations has been a special tournament for me and the Ireland team for lots of reasons - it's been fantastic for Irish rugby and for the whole country.
"To be voted RBS Player of the Championship by the fans makes it extra special but I'm really proud of our team effort right the way through the tournament and I would not be in this position if it was not for my team-mates.
"The support of the fans throughout our campaign has been unwavering and a huge part of the team's success on the pitch - I'm just glad we could reward them too by bringing home the Grand Slam."
It is the third year O'Driscoll has won the player accolade. He was voted RBS Player of the Championship in both 2006 and 2007.
The 2009 RBS Player of the Championship was decided as a result of a public vote, hosted on www.rbs6nations.com.
Members of Team RBS (former internationals Jason Leonard, Keith Wood, David Sole, Ieuan Evans, Philippe St Andre and Alessandro Moscardi) each put forward their three recommendations (in order of preference).
These were combined to create the shortlist: Delon Armitage, Lee Byrne, Jamie Heaslip, Paul O'Connell, Brian O'Driscoll, and Sergio Parisse.
Over 24,000 fans went online to cast their vote in the online poll - an increase of over 25% from 2008 - and O'Driscoll garnered nearly 30% of all the votes cast.
Like last year, Sergio Parisse (27.9%) was ranked in close second. O'Driscoll's Irish colleague O'Connell finished third.
Last year's RBS Player of the Championship was Shane Williams, who went on to amass a hoard of silverware, including the highly coveted IRB Player of the Year award.