United Nations specialized agency affiliated with but legally and financially distinct from the International Bank for Reconstruction and Development (World Bank) (World Bank). It was instituted in September 1960 to make loans on more flexible terms than those of the World Bank. IDA members must be members of the bank, and the bank's officers serve as IDA's ex officio officers. Headquarters are in Washington, D.C.

Most of the IDA's resources have come from the subscriptions and supplementary contributions of member countries, chiefly the 26 wealthiest. Although the wealthier members pay their subscriptions in gold or freely convertible currencies, the less developed nations may pay 10 percent in this form and the remainder in their own currencies.