The chairman of Bangladesh Bank told the BBC Yunus has been relieved of his duties as managing director of the microfinance Grameen Bank.
Muzammel Huq said Yunus failed to get the required approval from the board when he was appointed managing director in 1999.
Observers said the firing is the culmination of a long-running feud between Yunus and the government of Bangladesh, which owns a 25 percent stake in Grameen.
Grameen pioneered the microfinance concept of lending small amounts of money to the poor, a move that has been replicated worldwide.
A spokesman for Yunus promised a statement from the Nobel laureate would be issued.