Sergei Vasilyevich Ryakhovsky (Russian: Серге́й Васильевич Ряховский; 29 December 1962 – 12 November 2007) was a Soviet-Russian serial killer, convicted for the killing of 19 people in the Moscow area between 1988 and 1993.

In 1982, Ryakhovsky claimed he began to feel "an irresistible desire for intimacy with a woman", and made several attempts to rape elderly women in the Golyanovo area of east Moscow, for which he was convicted of hooliganism and received a four-year sentence in prison.

Despite his considerable strength and violent temperament, Ryakhovsky showed absolutely no resistance, later admitting that after seeing weapons in the hands of officers he became frozen with fear.

According to psychiatrists from the Moscow Serbsky Institute, Ryakhovsky's necrophiliac tendencies were caused by a malfunction in his central nervous system.

During the 1993 Russian constitutional crisis, Ryakhovsky, who supported the Supreme Soviet, wrote a letter to Alexander Rutskoy claiming that he was an innocent victim of the "anti-national authority".

However, in 1996 Russia imposed a moratorium on executions, instead the sentence was commuted to life imprisonment in a maximum-security penal colony in Sosnovka, Zubovo-Polyansky District, Mordovia.