The man called police at 12:18 p.m. and said he had just killed his wife, Sgt. Dave Linscomb said.
Police responded and found the man standing in front of his mobile home in the Rincon Valley Mobile Estates, Linscomb said.
Officers detained the man and found a deceased 64-year-old woman with a ligature around her neck lying on the living room floor, Linscomb said.
The couple were residents of the mobile home park off state Highway 12 east of Mission Boulevard, Linscomb said.
The suspect will be booked in the Sonoma County jail on suspicion of murder, Linscomb said.
Two Sonoma County deputy district attorneys and an investigator arrived at the tan, double-wide mobile home at 67 Cardinal Way late in the afternoon.
Some neighbors said they didn't know the couple well, but believed they had lived in the mobile home park for five or six years.