Philippe Moryoussef, a 50-year-old former senior derivatives trader, was found guilty of conspiracy to defraud by dishonestly manipulating Euribor - or Euro interbank offered rate - between January 2005 and December 2009 after an 11-week trial.
A conspiracy to defraud conviction carries a jail sentence of up to 10 years.
Reporting restrictions on the verdicts were lifted on Thursday after the jury failed to agree on a decision for co-defendants Carlo Palombo, an Italian-born former junior Barclays trader, Sisse Bohart, a Danish former Barclays junior trader and rate submitter and her former boss, Colin Bermingham.
A sixth defendant, 46-year-old former Deutsche Bank star trader Christian Bittar, a Frenchman who investigators said was once one of the world's best-paid traders, pleaded guilty before the trial began. He is already in custody.
Brussels-based Euribor is a benchmark for interest rates on around $150 trillion to $180 trillion of financial contracts and consumer loans worldwide.
(Reporting by Kirstin Ridley; Editing by Silvia Aloisi/Keith Weir)
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)