The biggest fines were handed to Citi and RBS, which will owe about €310.8 million ($348 million) and €249.2 million ($279 million), respectively.
The Commission said traders exchanged sensitive information and coordinated their activities in chatrooms on Bloomberg terminals. That gave the traders access to privileged information that helped them decide what currencies to buy and sell, and when.
The currency market is a massive part of the global financial system, with trading averaging more than $5 trillion per day, according to the Bank for International Settlements.
“Companies and people depend on banks to exchange money to carry out transactions in foreign countries,” Margrethe Vestager, the Commission’s antitrust chief, said in a statement. “Foreign exchange spot trading activities are one of the largest markets in the world.”
The chat rooms, which had names such as “Three way banana split” and “Essex Express ‘n the Jimmy,” were active between 2007 and 2013.
JPMorgan, Citi, Barclays and RBS settled a similar inquiry with the US Department of Justice in 2015. The banks agreed to pay fines of more than $2.5 billion.
Citi and Barclays declined to comment Thursday.
JPMorgan said in a statement that it was “pleased to resolve this historical matter, which relates to the conduct of one former employee.”
“We have since made significant control improvements,” a spokesperson said.
MUFG said it is “committed to ensuring integrity and compliance with the regulatory authorities” and had “taken a number of measures to prevent this occurring again.”
RBS said the fine is “a further reminder of how badly the bank lost its way in the past” and that its “culture and controls have changed fundamentally” in the past decade.