Georgi Ivanov Markov (March 1, 1929 - September 11, 1978) was a Bulgarian dissident who was assassinated in London by agents of the Bulgarian secret police assisted by the KGB. On September 7, 1978 he walked across Waterloo Bridge, which crosses the River Thames, and was waiting at a bus stop on the other side, when he was jabbed in the leg by a man holding an umbrella. The man apologised and walked away. Markov would later tell doctors that the man had spoken in a foreign accent.

Markov remembered feeling a stinging pain from where he had been hit by the umbrella tip, and when he arrived at work at the BBC World Service offices he noticed a small red pimple had formed and the pain from being jabbed had not gone away. By the evening he had developed a high fever, and died in agony three days later.

After his death, doctors found a small platinum pellet, some 1.5mm across, embedded in his calf. Further examination found that it had two small holes drilled in it, which contained traces of the poison ricin.

Markov had worked as a broadcaster and journalist for the BBC World Service since his defection from Bulgaria, then a communist state under the leadership of President Todor Zhivkov. He had criticised the regime many times on radio, and it is speculated that as a result of this, the Bulgarian government had asked the KGB to assist them in disposing of him.

Several high profile KGB defectors, such as Oleg Gordievsky have confirmed that the KGB was behind the assassination, even presenting the Bulgarian assassin with alternatives such as a poisonous jelly to smear on Markov's skin, but to this day no-one has been charged with Markov's murder, largely because most documents pertaining to Markov's death were probably destroyed.