I have yet to understand why people post questions like this in the forum. Directly from www.phpbb.com/features.php
(linked to from EVERY phpBB.com page...)
Database Server Support
* phpBB uses a database abstraction layer to enable seamless support of several database servers:
o MySQL 3.2x,
o PostgreSQL 7.x,
o Microsoft SQL Server 7/2000
o Microsoft Access (via ODBC)
o ...with more databases available in the future.
Why is it THAT hard to do a little research instead of relying on others to do it for you?