The official currency of Ukraine is the hryvnia which is abbreviated as UAH. The current official exchange rate can be found at the National Bank of Ukraine website
Hryvnias are required to pay for goods and services in Ukraine. Foreign currency can be easily exchanged at banks and numerous exchange bureaus throughout the country. Exchange points will not accept worn or torn bills.
Exchange terminals and ATMs issuing dollars and euros are slowly being rolled out. Credit cards are widely accepted (American Express less so) and contactless payment is becoming increasingly popular.