Yes you will, but it’s not something you should worry too much about.
The city of Vienna requires hotels, B&Bs and others to pay Ortstaxe when they rent out a room to you. This is a local tourist tax used to help finance the Vienna tourist board.
The rate at the time of writing is 3.2% of the accommodation cost (not including sales tax, cost of breakfast and an 11% Ortstaxe-free amount).
So, for example, a hotel would have to charge around €2.5 local tax on a room costing €100 without breakfast. Even those renting out their private apartments to visitors have to pay Ortstaxe (unless the occupants stay for over 3 months).
The relatively small amount is one reason not to worry too much about the tax.
Another is that local law requires that the Ortstaxe status is made clear in displayed prices, so you should always know where you stand.
Many (most?) quoted prices you see on hotel websites, for example, already include this tax. In German, the designation “inkl. Ortstaxe” after a price indicates this is so. In English, “local tax” is the common translation used.
So, for example, “Preise pro Zimmer, inkl. Ortstaxe” means “prices per room, including local tax”.
P.S. This tax is regional, so different rules may apply outside of Vienna.
(Photo credit: © djoronimo / Fotolia)