The pandemic is compounding the forces of conflict and climate change, which were already slowing poverty reduction, the bank said.
By 2021, this could rise to as many as 150 million, it added.
Extreme poverty is defined as living on less than $1.90 (£1.50) a day.
The projected increase would be the first since 1998, when the Asian financial crisis shook the global economy.
Before the pandemic struck, the extreme poverty rate was expected to drop to 7.9% in 2020.