Your age on election day is what matters.
Someone turning 18 on election day has reached the minimum age. Someone whose birthday is the following day has not yet met it for that election. A young person cannot vote locally in Hessen simply because another federal state has a lower voting age.
Subject to the other statutory conditions, German citizens and citizens of other EU member states can vote. Normally, they must have lived in the relevant municipality or county for at least six weeks; the law also covers habitual presence without a registered residence. Where someone has several homes, the main residence counts. They must not be excluded from voting by a court ruling.

The other three answers
All the options are ages in years, but only 18 matches Hessen’s rule.
14
At 14, the age requirement is not met. Political interest or participation in a youth body does not replace this voting right.
16
Sixteen is incorrect for this question about local elections in Hessen. Voting ages differ by state and type of election.
20
You do not have to wait until 20. If all the conditions are met, the right to vote starts at 18.
Check voting and standing as a candidate separately.
Active voting rights mean being allowed to cast a vote. Eligibility to stand means being allowed to be elected. For the local representative bodies discussed here, the minimum candidate age is also 18, but the normal local residence or presence requirement is three months rather than six weeks. Other disqualification rules must also be considered.
A residence permit alone does not automatically confer local voting rights. Conversely, citizens of other EU states do not first have to become German citizens. This explanation concerns the local elections described here, rather than a universal age rule for every election or participation scheme.
Section 30 · Right to vote · Hessen’s municipal code ↗Hessen + local election = from 18.
Check the state and election type first, then the minimum age. That avoids applying another jurisdiction’s rule to Hessen.
Three words for this question
- das aktive Wahlrechtright to vote
- The right to cast a vote.
- die Wählbarkeiteligibility to stand
- Legal eligibility to be elected.
- die Hauptwohnungmain residence
- Where someone has several homes, the main one under registration law.
