Richard Ramirez dubbed Night Stalker,[1] Valley Intruder (as his attacks were first clustered in the San Gabriel Valley), and Walk-in Killer was an American serial killer whose crime spree took place in California between June 1984 and August 1985. He was convicted and sentenced to death in 1989. He died in 2013 while awaiting execution.

Ramirez's childhood is considered an influence on his crimes. Abused by his father, Ramirez began developing gruesome, macabre interests in his early and mid-teens from his older cousin, Miguel ("Mike") Ramirez, who allegedly also taught him some of the military skills that he would go on to use during his year-long killing spree. Ramirez also cultivated a strong interest in Satanism and the occult. By the time he had left his home in Texas and moved to California at the age of 22, he had begun frequently using cocaine. Ramirez would often commit burglaries to support his drug addiction, many of which were later frequently accompanied by murders, attempted murders, rapes, and assaults.

Ramirez's highly publicized home invasion and murder spree terrorized the residents of the Greater Los Angeles area and later the San Francisco Bay Area over the course of fourteen months. However, his first known murder occurred as early as April 1984; this crime was not connected to Ramirez, nor was it known to be his doing, until 2009. Ramirez used a wide variety of weapons and different murder methods, including handguns, various types of knives, a machete, a tire iron, and a claw hammer. He punched, pistol whipped, and strangled many of his victims, both with his hands and in one instance a ligature; stomped at least one victim to death in her sleep, and tortured another victim by shocking her with a live electrical cord. Ramirez also enjoyed frequently degrading and humiliating his victims, especially those who survived his attacks or whom he explicitly decided not to kill, by forcing them to profess that they loved Satan, or telling them to "swear on Satan" if there were no more valuables left in their homes he had broken into and burglarized.

In 1989, Ramirez was convicted of thirteen counts of murder, five attempted murders, eleven sexual assaults, and fourteen burglaries.[2] The judge who upheld Ramirez's nineteen death sentences remarked that his deeds exhibited "cruelty, callousness, and viciousness beyond any human understanding".[3] Ramirez never expressed any remorse for his crimes. He died on June 7, 2013, of complications from B-cell lymphoma while awaiting execution on California's death row.[1]