These prepositions
only speak Genitiv.

Some prepositions need you to check the verb, and others need you to ask Wo? or Wohin?, but this group doesn't require either → wegen, trotz, während and the others in this group always take the Genitiv. You don't weigh the context or ask a question here; spotting the preposition already tells you the case.

Also: For fixed Dativ and Akkusativ prepositions, see These prepositions only speak Dativ and These prepositions only speak Akkusativ.

The list

Preposition	Meaning
wegen	because of, due to
trotz	despite, in spite of
während	during
statt / anstatt	instead of
aufgrund	due to, on the basis of
innerhalb	within, inside of
außerhalb	outside of
bezüglich	regarding, with respect to
infolge	as a result of

What Genitiv does to articles

The Genitiv changes the article. This is the one place where masculine and neuter pick up an -s or -es ending on the noun itself. Feminine and plural don't add that ending, but the article still changes.

Gender	Nominativ	Genitiv
masculine	derMann	desMannes
neuter	dasWetter	desWetters
feminine	dieArbeit	derArbeit
plural	dieKinder	derKinder

One thing worth noting: feminine Genitiv uses der, the same form as masculine Nominativ. Context tells you which one it is.

In sentences

Example	Preposition
Ich bleibe wegendes Wetters zuhause.	wegen + Genitiv
Er kam trotzder Kälte.	trotz + Genitiv
Wir arbeiten währenddes Meetings.	während + Genitiv
Sie trinktTee stattdes Kaffees.	statt + Genitiv
Wir warten aufgrundder Störung.	aufgrund + Genitiv

wegen + Genitiv

In careful written German wegen takes the Genitiv. wegendes Regens, because of the rain. The same applies to the rest of this group → trotz, während, statt. Write the Genitiv and you are always right.

The exception: spoken German reaches for the Dativ

This is the one place where everyday speech has moved away from the rule, and you will hear it constantly. It is not sloppy German: the forms below are in the dictionary, and in the first two the Dativ is the only normal option.

What you hear	Why
trotzallem	fixed phrase; the Genitiv trotz allen is not used
wegenmir	pronouns take the Dativ here
wegenUmbau	bare noun, no article to carry a Genitiv ending
währenddrei Jahren	plural with no article

So the safe rule stands: use the Genitiv when you write. But when you hear wegen dem Wetter instead of wegen des Wetters, nobody has made a mistake. That is simply how the preposition behaves out loud.

Register note

Several of these prepositions, especially bezüglich, aufgrund, and infolge, belong mostly to written and formal German. You'll see them constantly in business correspondence, legal texts, and academic writing. In conversation, wegen, trotz, and während are the ones you actually need to produce.