Why is it der Belgrader?

Belgrader ends in -er, and most nouns ending in -er are masculine: in a German dictionary, 86% of them take der.

All nouns ending in -er
Sense 1
der

Meaning

[1] inhabitants of the city of Belgrade

[1] Einwohner der Stadt Belgrad

Examples

[1] Many Belgraders used the nice weekend to walk in the surrounding area to walk in the vicinity

[1] Viele Belgrader nutzten das schöne Wochenende, um in der näheren Umgebung spazieren zu gehen.

Declension

1 Singular Plural
Nominativ der Belgrader die Belgrader
Genitiv des Belgraders der Belgrader
Dativ dem Belgrader den Belgradern
Akkusativ den Belgrader die Belgrader

Pronunciation

Dictionary entries include material from Wiktionary. Wiktionary