In Estonia, citizenship law is regulated by the Citizenship Act enacted in January 1995 and based on the principle of ius sanguinis. Estonian citizenship can be acquired by birth, by naturalisation and through achievements of special merit. Citizenship is acquired automatically by birth provided that one of the parents holds Estonian citizenship. In terms of naturalisation, this is regulated by Article 5-15 of the Citizenship Act which holds that one must pass an Estonian language test and have lived in Estonia for at least five years (must be a temporary resident for 8 years) before applying for naturalisation. Estonian citizenship can also be acquired for achievements of special merit to the Estonian state, defined as achievements which contribute to the international reputation of Estonia in areas such as science, culture or sports.
Under Article 1 of the Citizenship Act, Estonian citizens are not allowed to hold the citizenship of another country and no third country national can become Estonian without renouncing their original citizenship. Under recent amendments to the Citizenship Act, children born to stateless parents in Estonia will become Estonian citizens by naturalization at the moment of birth. Children born with dual citizenship need to renounce either the Estonian or their other nationality within three years of the person becoming an adult. Nonetheless, these changes are not sufficient to allow for dual citizenship for all citizens under Estonian law.