Arthur Budovsky, 42, ran his Costa Rica-based company, Liberty Reserve, from 2005 to 2013. Once registered with Liberty, people could transfer money to other users.
Deposits were converted into Liberty Reserve Dollars or Liberty Reserve Euros - which were tied to the value of the US dollar and the euro - or to ounces of gold. Prosecutors claimed the service enabled criminals to store and launder the proceeds of illegal activity by acting as a "financial hub".
The US Department of Justice said that by the time it was shut down it had more than 5.5m user accounts and had processed more than 78 million financial transactions with a combined value of more than $8bn.
As part of a plea agreement, Budovsky admitted laundering between $250m $550m in criminal proceeds linked to Liberty Reserve accounts based in the US.