The attack happened in Rochdale, Greater Manchester, as the pensioner walked to a local shop.
The victim felt a hand go over her mouth and she was hauled backwards in Spotland Road at about 6.45am yesterday, police said.
Greater Manchester Police want to hear from anyone who may have seen the victim, and potentially the offender
The pensioner is white and wore a white summer dress with a flower print and a cardigan.
Due to the nature of the attack, the only description of the offender is that he was white.
Superintendent Alistair Mallen said: "I am sure the entire community will share our revulsion at this. The victim has been through an horrific ordeal and we are all hoping she can make a full recovery. She is now being supported by experienced officers and we are doing everything possible to reassure her that we will catch the man responsible.
"This kind of attack is thankfully so rare that it will naturally cause a huge amount of concern in the community.
"I now want people, including the criminal fraternity, to imagine if that had been your mum or grandma. I want to harness these feelings and use them to help the police do their job - catch this man and put him before the courts."
Anyone with information should call police in Rochdale on 0161 856 8470/8420 or Crimestoppers on 0800 555 111.
Simon Danczuk, Labour MP for Rochdale, said there was "a real sense of shock and horror" in the community over the attack.
He said: "Local people are struggling to comprehend how anyone could do this. Our heart goes out to this poor woman. She must have gone through hell.
"There is a real sense of shock and horror in the community and the police need to do everything possible to catch this sick individual. But they need the help of the community and people must stand up and be counted.
"Someone somewhere will know something that can help the police and I would urge them to search their conscience and come forward to pass that information on.
"Sexual abuse has left painful scars on our town in recent years and we are determined to confront this crime and make sure anyone connected to this type of activity is jailed.
"There is a huge amount of anger across the town and we need to unite to help ensure that criminals like this have no place to hide. Anyone with even a glimmer of suspicion should contact the police immediately."