Ramirez was on death row at San Quentin. He died at nearby Marin General Hospital, the department said in a written statement.
Ramirez was sent to prison in 1989 after being convicted of 13 murders plus additional counts of attempted murder, sexual assault and burglary. His crime spree across the Los Angeles region and the San Francisco Bay area in the mid-1980s lasted for months and terrorized the state.
The apparently peaceful demise early Friday was in stark contrast to the sensational attacks he was convicted of. Ramirez struck in the wee hours in quiet neighborhoods, gaining entry through unlocked windows and doors.
The victims included several senior citizens. Most of the victims were shot dead but others were strangled or had their throats slashed.
Police found satanic pentagrams painted on the walls by the intruder. The Los Angeles Times said Ramirez was a professed satanist.
The Times said gun and ammunition sales increased in Los Angeles County during the crime wave.
Ramirez was captured Aug. 31, 1985 when he was tackled by a group of citizens in East Los Angeles at the end of a 20-minute pursuit by police. Ramirez had tried to carjack a woman's vehicle but wound up being pummeled by four passersby, including at least one armed with a steel bar.
Angelina De La Torre, the woman whose car he tried to steal, told the Times she at first thought the attacker was an ordinary mugger until her friend bolted from the car screaming: "That's the Night Stalker! That's the Night Stalker!"
"Then I recognized the eyes from the news last night," De La Torre said. "I gave him the keys."