FRANKFURT — Alexandre Lamfalussy, a Hungarian-born economist and banker considered a founding father of the euro, died on Saturday in Ottignies, Belgium. He was 86.

His son Christophe confirmed his death but did not provide the cause.

Mr. Lamfalussy was the founding president of the European Monetary Institute, which later became the European Central Bank and which now oversees the eurozone monetary system.

As president of the institute, Mr. Lamfalussy assembled the core of the multinational staff that started the common currency, and he gave the euro much of its intellectual underpinnings. He helped devise the rules on debt and spending that govern membership in the eurozone and was even involved in designing the bank notes.

“Alexandre Lamfalussy’s name will always be inextricably connected with the single currency and the European Central Bank,” the central bank said in a statement on Monday. “He guided the immense and unprecedented preparatory work for the establishment of the E.C.B. in July 1998 and the launch of the single currency in January 1999.”