Ennis will go up against British record holder Tiffany Porter over the sprint hurdles and in-form Shara Proctor in the long jump.
"The great thing about the Aviva 2012 Trials is that I'll be taking on specialists and they will all be fighting for Olympic spots," added Ennis. "Tiffany and Shara are world-class opposition and they've both had great starts to the year. "There will be no let up over two days and these are the type of battles that I will find at the Olympics."
Ennis is a four-time national champion and will defend the high jump title she won comfortably in 2011. This month's trials will be the biggest for two decades with over 750 of Britain's best athletes going head-to-head in the battle for selection.
"There is a depth in the sport that we have not seen for 20 years and we have a number of events where five or six athletes are competing for three places," said UK Athletics head coach Charles Van Commenee. "It doesn’t take a genius to work out the maths and athletes will need to be at the very top of their game at the Olympic Trials if they want to make the team for London 2012.”
* Back the team and watch over 750 of Britain’s best athletes in action at the Aviva 2012 Trials at the Birmingham Alexander Stadium from 22nd-24th June. For tickets visit www.uka.org.uk/aviva-series or call 08000 55 60 56.