Also nominated are back rowers Wycliff Palu and David Pocock, utility back Adam Ashley-Cooper, scrum-half Luke Burgess, second row Nathan Sharpe and the man who kicked Australia to a famous win in South Africa in this year's Tri Nations, Kurtly Beale.
Giteau is attempting to become the first player to receive the honour in successive seasons, while 2007 winner Sharpe hopes to build on his runners up position last time out.
The medal will be presented at the annual Australian Rugby Union awards night in Sydney on October 21.
The award is effectively a Players' Player of the Season, with voting taken from after each of the 15 Tests played by the Wallabies between last year's November tour and the end of the 2010 Tri Nations.
Each player in the matchday 22 casts votes on his three best players in the match on a 3-2-1 basis, with the overall winner the player with the highest tally at the end of the Australian season.
This year, the Australian Rugby Union and the Australian Rugby Union Players Association decided to unveil two voting updates during the season to heighten interest in the award.
Palu was out in front following the five Test matches against New Zealand, England, Ireland, Scotland and Wales last autumn but injury since ruled him out of the remainder of the season.
Openside flanker Pockock then took over the running by the time of the second announcement after the June Tests against Fiji in Canberra, England in Perth and Sydney and Ireland in Brisbane.
Prior to the start of the Tri Nations, current holder Giteau trailed Pocock by three points, with Cooper in third place ahead of Palu and Genia.
John Eales Medal winners
2002 - George Smith
2003 - Phil Waugh
2004 - David Lyons
2005 - Jeremy Paul
2006 - Chris Latham
2007 - Nathan Sharpe
2008 - George Smith
2009 - Matt Giteau