As of 2017, visa-free entry via the Minsk National Airport has been introduced for citizens of multiple world countries. The visa-free period has recently been extended from 5 days to 30; if your stay will last longer than 5 working days, you will also need to register with local authorities and pay a small registration fee.
In order to make use of visa-free entry, travelers must arrive and exit solely through the Minsk National Airport (no border crossing by car or train allowed). This does not apply to flights to and from Russia: those crossing the border from or into Russia will need to obtain a visa in advance.
Those eligible for the 30-days visa include all nationals of the European Union and further European countries, as well as the United States, Canada, Australia, Japan, and many others.
For longer stays a visa will most definitely be required. To learn more about different types of visas and supporting documents for each type, visit: http://mfa.gov.by/en/visa/typesofvisa