The 19-year-old midfielder recently underwent ankle surgery, which will keep the player out of action for at least 22 weeks.
"Wilshere will be ready for Euro 2012," Wenger confirmed.
"He will spend 12 weeks in a boot and after that it is rehab. Twelve weeks brings us to around Christmas. If all goes well, you would think he will be fit again to play in half the time you are in the boot.
"Count ten weeks to be closer to the truth, so it's 22 weeks to be capable to play football again."
Wlshere made his senior England debut against Hungary in August 2010.