Police arrived at the home in Santa Ana after 10 a.m. Thursday. They found the house secure with the woman's car present.
They forced entry and found the woman deceased in her bedroom.
The woman was reportedly in her 40s or 50s, but was not identified.
Santa Ana Police Cpl. Anthony Bertagna said the woman had not died from natural causes, but said it was not known how the woman died, and wouldn't be known until an autopsy was performed.
Police are proceeding with a homicide investigation.
Bertagna said there were no suspects, but said there were no signs of forced entry, suggesting an attacker was known to the woman or a suspect had a key to the house.
Bertagna said there was one other resident of the home, but that person was not identified.
Police did not have a motive for the murder, saying the investigation was in its early stages.