A Bulgarian umbrella is an umbrella with a hidden pneumatic mechanism which injects a small poisonous pellet containing ricin. It has a hollowed stalk into which the pellet neatly sits.
Such an umbrella was allegedly used in and named for the assassination of the Bulgarian dissident writer Georgi Markov on 7 September 1978 (the birthday of the Bulgarian State Council chairman Todor Zhivkov, who had often been the target of Georgi Markov's criticism) on Waterloo Bridge in London. Markov died three days later. It was also allegedly used in the failed assassination attempt against the Bulgarian dissident journalist Vladimir Kostov the same year in the Paris Métro. The poison used in both cases was ricin. Both assassination attempts are believed to have been organized by the Bulgarian Secret Service of the time of the Cold War with the assistance of the KGB.
These two cases inspired the 1980 French film Le Coup du parapluie (The Umbrella Coup) directed by Gérard Oury, starring Pierre Richard and Bulgarian writer Stefan Kisyov to write his novel The Executioner. A type of this umbrella is used even in poliziottesco Italian movie The Police Can't Move in 1975.
A Bulgarian umbrella was featured in the 2013 The Americans episode, "The Clock". A similar assassination (and attempt) were central to the plot of the 1978 Quincy, M.E. episode, "Hot Ice". The 2010 episode "Marionette" of Fringe begins with an organ thief administering a paralytic with an umbrella.