Why is it die Aller?

Aller ends in -er. Most nouns with this ending are masculine (86% take der), but Aller is an exception: die Aller.

The other -er exceptions
Sense 1
die

Meaning

[1] A 263 km river in Saxony-Anhalt and Lower Saxony, Germany's right tributary of the Weser

[1] ein 263 km langer Fluss in Sachsen-Anhalt und Niedersachsen, Deutschland; rechter Nebenfluss der Weser

Examples

[1] We used to be on all of the canoe

[1] Wir sind früher oft auf der Aller Kanu gefahren.

[1] We crossed the everyone

[1] Wir überquerten die Aller.
More source examples (1)

These dictionary examples can include historical and less common uses.

[1] The children tried to swim in the everyone

[1] Die Kinder versuchten, in der Aller zu baden.

Declension

1 Singular Plural
Nominativ die Aller —
Genitiv der Aller —
Dativ der Aller —
Akkusativ die Aller —

Pronunciation

In context

Dictionary entries include material from Wiktionary. Wiktionary