The Naturalization is regulated by Nationality Act Germany.

A foreign national who was been lawfully residing in Germany for at least eight (8) years and who meets the prerequisites listed hereinafter may, upon his or her application, be naturalized on the basis of the responsible authorities’ discretion. For persons qualifying for political asylum, other refugees, and stateless persons the mandatory period of prior lawful residence in Germany has been reduced to six (6) years, whereas for foreign nationals married to Germans the mandatory period of prior lawful residence in Germany has been reduced to three (3) years. Additionally, the mandatory period of prior lawful residence in Germany will be reduced to seven (7) years in cases where the integration course has been successfully completed. An additional reduction of the mandatory period of prior lawful residence in Germany to six (6) years may be granted upon proof of extraordinary integration efforts (German language proficiency considerably above the "German Certificate" level or outstandingly active civic involvement such as e. g. by joining a volunteer fire brigade or sports club).
As a general rule, the foreign national must be capable of assuring his dependent family members' subsistence out of his or her own resources. The foreign national must not have a criminal record and needs to establish proof of adequate proficiency in the German language.