Spanish nationality law is based on the principle of jus sanguinis (right of blood), meaning that nationality is primarily acquired through a person's parents rather than by birth within the territory. Here are the key details and principles of Spanish nationality law:

Acquisition of Spanish Nationality

By Origin (Jus Sanguinis):

• Spanish Parents: A child born to at least one Spanish parent acquires Spanish nationality at birth, regardless of the place of birth.
• Foreign Birth: A child born abroad to a Spanish parent may acquire Spanish nationality by declaration at the Spanish consulate or through a process called "option" during their minority or later.

By Residence:

General Rule: Foreign nationals can apply for Spanish nationality after residing legally in Spain for a certain period (usually 10 years, reduced in some cases to 1 or 2 years for specific groups like refugees, stateless persons, or those born in Spain with a continuous residence). Marriage to a Spanish Citizen: Foreign spouses of Spanish citizens can apply for Spanish nationality after residing legally in Spain for one year.
By Option:

• Minors: Children born to foreign parents in Spain may opt for Spanish nationality after residing legally in Spain for two years and fulfilling certain conditions.
• Adults: Foreign nationals who have been under the legal guardianship of a Spanish citizen or who were adopted by a Spanish citizen may also opt for Spanish nationality.

By Special Circumstances:

• Sephardic Jews: Descendants of Sephardic Jews expelled from Spain in 1492 have the right to apply for Spanish nationality.
• Latin Americans: Nationals of Latin American countries, Andorra, the Philippines, Equatorial Guinea, or Portugal may be granted Spanish nationality after two years of legal residence in Spain.

Loss and Renunciation of Spanish Nationality

• Loss: Spanish nationality can be lost by acquiring another nationality with the intention of renouncing Spanish nationality, or by residing abroad for more than three years while holding another nationality acquired before residing abroad.
• Renunciation: Individuals who acquire Spanish nationality by option or residence may renounce it, provided they are of legal age.

Dual Nationality

• Spain generally allows dual nationality, meaning individuals do not need to renounce their original nationality to acquire Spanish nationality. However, this can vary based on the laws of the individual's original country of nationality.

Process and Documentation

• Applying for Spanish nationality typically involves submitting an application to the Civil Registry, providing documentation such as birth certificates, proof of residence, and other specific documents depending on the basis of application (parentage, residence, etc.). The process is overseen by the Ministry of Justice and administered by Civil Registries and consular offices abroad.

For the most accurate and detailed information, including specific requirements and forms, it is advisable to consult with a legal professional specializing in Spanish immigration law or visit the official website of the Spanish Ministry of Justice or Ministry of Interior.