By naturalization abroad
If you willingly apply for a foreign citizenship and obtain it, German citizenship is automatically lost. However, since 28.08.2007 (date of naturalisation in the foreign country), German citizenship is not lost anymore if you apply for and receive the citizenship of an EU member state or of Switzerland.
In all other cases, loss of citizenship can be avoided by obtaining a special permit ("Beibehaltungsgenehmigung") before you are naturalised in a foreign country.
Information about Beibehaltungsgenehmigung
The marriage of the parents of a child born out of wedlock was called “legitimization”. The legitimisation by a foreign father could lead to the loss of a child’s German citizenship.
The Federal Administrative Court in Leipzig decided with court decision of November 29, 2006 that the legislation regarding the loss of German citizenship in case of legitimisation through a foreign citizen with retrospective effect since April 1, 1953 is no longer applicable. This means that children born out of wedlock to a German mother, who have been legitimated by a foreign citizen after March 31, 1953, have NOT lost their German citizenship.
German women, who married a foreign citizen before May 23, 1949, have lost their German citizenship even if they became stateless. They can be re-naturalised if certain requirements are met.
German women, who married a foreign citizen between May 23, 1949 and March 31, 1953, have lost their German citizenship only if they did not become stateless. Since April 1, 1953 German citizenship cannot be lost by marriage with a foreign citizen any more.
(Since 01.01.1977): If you are adopted by a non-German and are no longer considered to be legally related to your German parent(s), you lose German citizenship if the adoption automatically makes you a citizen of your adopted parents' country.
By voluntarily entering into the armed forces or other armed units of a country whose citizenship you also have
Loss of German citizenship by entering foreign armed forces can only be avoided with an official permission from the competent German authorites.
However, as of July 6, 2011 (date of commencement of duties), this permit is automatically given to dual nationals who also hold the citizenship of
- another EU member state
- an EFTA member state
- a NATO member state or
- a state listed in § 41 I of the German "Aufenthaltsverordnung" (Australia, Israel, Japan, Canada, Republic of Korea, New Zealand, United States of America)
and who serve in this country.
By renunciation (if you hold dual citizenship)
If you are holding dual citizenship (German and at least one other citizenship), you can renounce the German citizenship by declaration.
By permanent residence abroad before 1914
German citizen who had their permanent residence abroad for more than 10 years before 1914 automatically lost their German citizenship unless they registered themselves in the “Konsulatsmatrikel” (consular register) of the German consulate. This reason for loss of German citizenship is particularly important in case you wish to trace back German citizenship to ancestors who emigrated Germany before 1904. If this is the case, they would have lost German citizenship after 10 years and could not have passed it on by descent to future generations.