This is a subjective selection, but I will also mention a tourist highlight at the end.
First things first, around here we mostly call x-mas markets “Christkindlmarkt” and there is no entrance fee to any of them. Since the city is literally plastered with one “Adventmarkt” next to the other, I’m sure you’ll find one that fits your taste!
#1 Art Advent at Karslplatz (above picture)
is not only special for its very romantic and kid friendly (play area on straw and petting zoo in the center) setting, but also for its craft goods one can purchase after one or two “Glühwein” or “Punsch” – all food and drinks at the Art Advent market are fully organic.
Tucked away in tiny alleys up the Spittelberg hill, this is a true gem I’ve loved to go to ever since. It might get crowded, and surely will on weekends, but this way you won’t feel so cold. Make sure to check out the lovely courtyard of Amerlingbeisl!
#3 Weihnachtsdorf at university campus Altes AKH
I used to study at this campus site (Vienna is a student city with many universities, and their departments are spread out all over the city) and still like to go back – and not only for the Christkindlmarkt.
Not letting you down on the touristy, overcrowded and overpriced famous markets: Christmas Dream, they call it now, in front of the admittedly beautiful city hall is the biggest of all Christmas markets in Vienna.