If you are a German citizen and you obtain a foreign citizenship by application, you will normally automatically lose your German citizenship. However, as of 28 August 2007 obtaining the citizenship of an EU member state or of Switzerland by application will not lead to the loss of German citizenship.
In all other cases, loss of citizenship can be avoided by obtaining a retention permit (Beibehaltungsgenehmigung, please see Retention of German citizenship) before you are naturalised in a foreign country.
In some cases, German citizenship can be lost by marriage
German women who married a foreign citizen before 23 May 1949 lost their German citizenship even if they thereby became stateless. German women who married a foreign citizen between 23 May 1949 and 31 March 1953 lost their German citizenship only if they did not become stateless. They can be renaturalised subject to certain requirements. Please see Renaturalisation and discretionary naturalisation for more information.
As of 1 April 1953 marriage to a foreign citizen does not lead to loss of German citizenship.
In some cases, German citizenship can be lost by adoption
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 the adopting parent’s country. If this applies to you, please contact the Embassy in London or the General Consulate in Edinburgh.
If you hold dual citizenship you can renounce your German citizenship by declaration. See Renunciation of German citizenship.
In all other cases (e.g. loss of citizenship through legitimisation), please contact the Embassy in London or the Consulate General for further information.