An ISBN is an International Standard Book Number. It is a persistent identifier and unique, internationally used standard to identify books. The aim of the ISBN is to enable you to quickly and correctly find every published title in databases.

An ISBN is not legally required, but recommended if you want to offer your work to a more commercial market. 

You can request an ISBN online at boekenbank.be . You need a publisher's prefix to do this or you can request a one-time ISBN number. If you request an ISBN, you have to send two copies to the KBR.

Some faculties, like the faculty of Bio-Science and Engineering, request the ISBN for PhD students. This service is reserved for PhD students of that faculty. If your PhD dissertation contains confidential information, you can still request an ISBN. just make sure to explicitely mention your dissertation is confidential.