Quote Originally Posted by scottish-guy View Post
Ok it appears Latvia and CZ are out:

"As of October 2017, fifteen European countries legally recognise and perform same-sex marriage: Belgium, Denmark, Finland, France, Germany, Iceland, Ireland, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden and the United Kingdom. In Austria, marriages will be legal from 1 January 2019".

Out of those I don't know which ones would readily grant a Visa to a Vietnamese citizen. Denmark is mooted online as the easiest to get married in but the ease of obtaining the Visa is not stated and the list of documents required for a marriage is quite onerous
The whole idea of the Shengen zone is once you have a visa for one Shengen country, you can use it to legally enter all of them. A necessary step, since they don't have any border controls either.

So I think you need to:

1 Figure out which country grants a Shengen visa most easily.
2 Decide which Shengen country to get married in, quite separately.
3 I imaging marriage in one EU country has to be recognized in another, as anything else goes against the whole ethos of the organization.

Of course, please check my logic is right on points 2 & 3.