Charles Dallara, who led the private banks' side in grueling negotiations over writing down Greek debt, is stepping down as head of the Institute of International Finance, an IIF spokeswoman has said.
Dallara will stay on as head of the powerful global banking institute until year-end, to ensure an "orderly transition," spokeswoman Emily Vogl said.
His departure is not linked to the debt negotiations with Greece, which after months of stressful talks ended with private banks agreeing to write off more than €100 billion of Greek debt in March.
"After 19 years presumably the time had come to move on to something else," she said.
"It's a very long lead. There is nothing pressing. He's giving himself time for an orderly transition," she added.
The announcement that he will step down comes as worries increase that Greece could exit the euro zone despite the new bailout pact negotiated in March and April.
An exit could ultimately force creditors including banks to take greater losses on their Greek euro debt.
Last month Mr Dallara urged less fiscal pressure on Athens, warning that it could force a devastating Greek exit from the euro zone.
"The contagion effects on the rest of the Europe could be immense for Greece to leave the euro in a disorderly fashion," he said in Dublin.