The punishment came as a result of the help the bank gave to the company France Offshore, a financial manager that helped French citizens evade paying taxes at home via offshore entities and Rietumu bank accounts.
In addition former Rietumu bank chairman Alexander Pankov was given a four year suspended jail sentence.
The founder of France Offshore, Nadav Benoussan, was given a five-year jail sentence, of which three are suspended, plus a 3 million euro fine and a ban from the finance business.
In all 15 people including France Offshore's clients, staff and business partners received sentences.
As previously reported by LSM, Benoussan boasted of his jet-setting lifestyle as boss of France Offshore from 2008-2012 and even produced a promotional video showing him going to Reitumu bank with bundles of paperwork from clients.
Latvia was promoted as a place that could provide a tax haven for all, more user friendly and with fewer questions asked than Switzerland.
The huge size of the fine comes because French prosecutors estimate that at least 200 million euros and perhaps up to 850 million euros was hidden from the taxman in total. It is by far the largest penalty ever handed to a Latvian bank and is equivalent to Rietumu's entire profits for 2016.
The decisions are subject to appeal.
A statement from the bank given to LSM said:
"We will carefully examine the full text of the decision and together with our attorneys decide about further actions. At this moment it can be said that we strongly disagree with the decision and this decision will be appealed."