The man entered the woman's home in the Little Horton area of Bradford at about 5am today.
He grabbed hold of her arm and punched and pushed to the floor as she tried to fight back. He then left with cash that she was keeping in her property.
The woman was taken to hospital by ambulance and is continuing to receive treatment for shock.
The suspect is described as wearing all black and a balaclava.
Detective Inspector Amanda Middleton, of Bradford District CID, said: “Quite rightly, I believe this incident will cause outrage to the general public that someone would attack an elderly, vulnerable woman in her own home.
“I can ensure the local community that an extensive investigation is already under way and we are committed to identifying the perpetrator and ensuring they are brought to justice.
“As part of this investigation, we are keen to hear from anyone who heard or witnessed anything suspicious in the area around the time of this offence or with any information that could help us identify the person responsible for this cowardly and reprehensible crime.”
Anyone with information is asked to call Bradford District CID via 101, quoting crime reference 13180385212, or use the 101 Live Chat facility on the West Yorkshire Police website.
Information can also be given to independent charity Crimestoppers, anonymously, on 0800 555 111.