I am a Dutch citizen and want to visit South Korea.
Do I need a visa?
According to Timatic:
The following are exempt from holding a visa:
Nationals of Netherlands for a maximum of 90 days.
Visitors are required to hold proof of sufficient funds to cover their stay and documents required for their next destination.
You do not need a Visa.
Korea's Visa Exeption program allows holders of ordinary (tourist) passports from 67 countries to visit for up to 90 days without a visa. The Netherlands is one of those. Note that the specifics vary by country.
A second list covers countries like the US for which visa-free entry is allowed for up to 30/90 days.