At launch last year, Window Phone 7 supported 5 display languages: English (US and UK), French, German, Italian, and Spanish.

In the upcoming “Mango” update, 17 more will be added: Brazilian Portuguese, Chinese (simplified and traditional), Czech, Danish, Dutch, Finnish, Greek, Hungarian, Japanese, Korean, Norwegian (Bokmål), Polish, Portuguese, Russian, and Swedish.

Read the full announcement on the Windows Phone Blog.