Belgium appointed Koen Geens, a university professor, to replace Steven Vanackere who stepped down unexpectedly as finance minister early Tuesday.
A statement issued by the royal place said King Albert II "has nominated Koen Geens to serve as finance minister."
Defence Minister Peter Crem will take on the post of deputy prime minister which Vanackere also held, it said.
Geens, 55, is a professor at the respected Catholic University of Louvain where he specialises in corporate financial law, according to the school's website.
Vanackere resigned earlier Tuesday after being linked to a scandal concerning Belfius bank, Belga news agency said.
Vanackere denied any wrongdoing in an affair regarding the bank and a social organisation linked to his Flemish Christian-democrat CDV party, the agency added.
Vanackere, 49, was given the finance portfolio in December 2011 when Socialist Prime Minister Elio Di Rupo formed a coalition government after an almost two-year political vacuum during which Belgium remained in the hands of a caretaker government.
He served as foreign minister in that government for two years.
His name came up in the press over the January buyback by Belfius -- formerly Dexia Banque Belgique -- of 110 million euros worth of shares owned by two social organisations linked to his party, against a loan at preferential terms of 6.25 percent interest, plus a discreet 1.5 percent bonus.
The press said the deal was negotiated through a Belfius administrator who occasionally worked out of the minister's office.