1. Germany: This is the most obvious one! German is the official language of Germany, spoken by the vast majority of its population.
2. Austria: German is the official language of Austria, and is spoken by nearly all of the population.
3. Switzerland: German is one of the four official languages of Switzerland, along with French, Italian, and Romansh.
4. Liechtenstein: German is the official language of Liechtenstein, and is spoken by almost the entire population.
5. Luxembourg: Although Luxembourgish is the official language, German is also an official language and is widely spoken, especially in formal settings.
It's worth noting that while these are the only countries where German is an *official* language, it's also spoken as a minority language in several other countries, such as Belgium, Italy, and Namibia.