If you are an EU/EEA student you can enter Bulgaria with your ID document. If your stay exceeds 3 months you will have to obtain a temporary residence permit from the local police administration department.
Non EU/EEA citizens
If you come from a non EU/EEA country you can enter Bulgaria on the basis of a valid passport and a visa. The visa can be obtained from the Bulgarian consulate in your country of residence. Detailed information is available at all Bulgarian consulates in Europe.
For more information see: www.mfa.government.bg
Non EU/EEA citizens visiting Bulgaria for education and specialization are invited to submit at the Consular section of the Bulgarian Embassy in their country of residence a document that confirms the purpose of their visit in Bulgarian. The document (Udostoverenie) for a long-term visa (type D) is to be issued by the Bulgarian Ministry of Education and Science after the University has sent the complete set of the application documents of the approved candidate. In order to get admission and apply for visa type D in time, the applicants are encouraged to apply at the University no later than 15, September for the respective academic year.
After their registration at the respective Faculty of the University for the current academic year, the full-time students apply for a Bulgarian ID card for a long term residence at the Migration office of the Bulgarian Ministry of Interior.