In Russian, blat (Russian: блат) is a form of corruption which is the system of informal agreements, exchanges of services, connections, Party contacts, or black market deals to achieve results or get ahead.
In the Soviet republics, blat, a form of corruption, was widespread because of the common deficit of consumer goods and services. In Soviet times the price of consumer goods was dictated by the state rather than set by the free market which resulted in a consumer goods deficit leading to corruption. Blat was used to gain a prestigious position or a rewarding job or an overseas posting or enroll in a prestigious major in university bypassing fair and just selection processes. Blat was not readily accessible to the ordinary citizen; rather, only the elite or prestigious members of society were able to create these corrupt relationships with others. 
The system of blat can be seen as an example of social networks with some similarities to networking (especially 'good ol' boy' networks) in the United States, old boy networks in the United Kingdom and the former British Empire, or guanxi in China.
However, the noun blatnoy (блатной) has a criminal meaning in Russian and it relates to a status in the criminal world. It usually means a member of a thief gang, (Blatnoy/блатной) itself means professional criminal in Russian.
The word was primarily used to describe networks, when people made each a favour in exchange for another favour.
According to Max Vasmer, the origin of the word blat is the Yiddish blatt, meaning a "blank note" or a "list". However, according to both Vasmer and N. M. Shansky, blat may also have entered into Russian as the Polish loanword blat, a noun signifying "someone who provides an umbrella" or a "cover". The word became part of Imperial Russian criminal slang in the early 20th century, where it signified relatively minor criminal activity such as petty theft.
Blatnoy originally meant "one possessing the correct paperwork", which, in the corrupt officialdom of Imperial Russia and the Soviet Union indicated that the blatnoy was well connected.
In addition, the word blatnoy came to indicate career criminals because they had a blatnoy or special status in the Russian criminal underworld. The word is used to indicate association with the criminal underworld (e.g. "blatnoy language"/Fenya, "blatnoy behavior", "blatnoy outlook").
A notable operation of blat system was the institution of tolkachs. Because in the Soviet Union, the Gosplan wasn't able to calculate efficient or even feasible plans, enterprises often had to rely on people with connections, who could then use blat to help fulfill the quotas. Eventually most enterprises came to have a dedicated supply specialist – a tolkach (literally pusher) – to perform this task.
- Ledeneva, Alena V. (1998). Russia's Economy of Favors: Blat, Networking and Informal Exchange. Cambridge Russian, Soviet and Post-Soviet Studies. Cambridge University Press. p. 1. ISBN 0-521-62743-5.
- Hsu, Carolyn, L. (September 2005). "Capitalism without contracts versus capitalists without capitalism: Comparing the influence of Chinese guanxi and Russian blat on marketization". Communist and Post-Communist Studies. 38: 309–327 – via Science Direct.
- Ledeneva, Alena V. (1998). Russia's Economy of Favors: Blat, Networking and Informal Exchange. Cambridge Russian, Soviet and Post-Soviet Studies. Cambridge University Press. p. 52. ISBN 0-521-62743-5.
- Yang, Mayfair Mei-Hui (January 1989). "The Gift Economy and State Power in China". Comparative Studies in Society and History. Cambridge University Press. 31: 47–48. JSTOR 178793.
In blat, there is a 'personal basis for expecting a proposal to be listened to,' while bribery is conceived of as a relationship linked only by material interest and characterized direct and immediate payment. In the Chinese cultural discourse, there is on the one hand often a fine line between the art of guanxi and bribery (xinghui).
- Ledeneva, Alena V. (1998). Russia's Economy of Favors: Blat, Networking and Informal Exchange. Cambridge Russian, Soviet and Post-Soviet Studies. Cambridge University Press. p. 12. ISBN 0-521-62743-5.
- Ledeneva, Alena V. (1998). Russia's Economy of Favors: Blat, Networking and Informal Exchange. Cambridge Russian, Soviet and Post-Soviet Studies. Cambridge University Press. p. 25. ISBN 0-521-62743-5.