The 82-year-old was found in the front yard of a George Street home about 8.30am (AEST) today.
She's been taken to Rockhampton Base Hospital where she remains in a critical condition.
She had extensive injuries and was covered in a white powder, possibly from a fire extinguisher which may have been used in the attack, the Courier-Mail reports.
Rockhampton district officer detective inspector John Wacker said the woman was allegedly attacked with blunt object and then sexually assaulted.
"I think it's a sick, cowardly, vicious attack on a defenceless lady who is an 82-year-old grandmother," he said.
The victim's son told Channel Nine he couldn't recognise her by her face.
"She's a very good and honest little woman, the sort of woman that shouldn't happen to, that's for sure," he said.
He also said his mother would have put up a fight.
"She's tough, that may be why she got the injuries she did, you don't know," he said.
"I'd like to get a hold of him before the police got him that's for sure, I think anyone would like to do that.
Police have called in the dog squad to hunt for the offender.
The man is described as being Aboriginal or Torres Strait Islander in appearance, about 172cm tall with dark shoulder-length hair, a moustache and goatee. He was wearing a black t-shirt underneath a red flannelette shirt and three-quarter length denim shorts.
Anyone with information which could assist police should contact Crime Stoppers on 1800 333 000.Source