De or het postimpressionist?

The correct Dutch article is:

de postimpressionist

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

How to use postimpressionist

the postimpressionistde postimpressionist
this postimpressionistdeze postimpressionist
that postimpressionistdie postimpressionist
our postimpressionistonze postimpressionist
your postimpressionistjouw postimpressionist
every postimpressionistelke postimpressionist
which postimpressionist?welke postimpressionist?
a big postimpressionist / the big postimpressionisteen grote postimpressionist, de grote postimpressionist