De or het regiovergadering?

The correct Dutch article is:

de regiovergadering

Rule Words ending in -ing: almost always de. See the rule

How to use regiovergadering

the regiovergaderingde regiovergadering
this regiovergaderingdeze regiovergadering
that regiovergaderingdie regiovergadering
our regiovergaderingonze regiovergadering
your regiovergaderingjouw regiovergadering
every regiovergaderingelke regiovergadering
which regiovergadering?welke regiovergadering?
a big regiovergadering / the big regiovergaderingeen grote regiovergadering, de grote regiovergadering