You can't apply to become a Portuguese citizen unless you qualify legally under law in that country. Portugal has a few different avenues for citizenship, mainly being born to a citizen, marrying a citizen and moving to Portugal for a length of time. Sometimes children born in Portugal to non-citizens are also eligible for citizenship, but usually only if the parents have valid residence permits and have lived in Portugal for at least six years. Children adopted by Portuguese citizens are automatically eligible for citizenship, as of January 2011.
Move to Portugal with a valid Passport from your home country. Start a job search. Register with the Social Security office and get a tax code before starting. The tax code is available from the the local branch of the Director General of Taxes in your local area and Social Security offices are located throughout the country. You'll need your passport, tax returns for the past year years and a tax identification number from your home country. Once you have a job, apply for a Work and Residence Visa at the local consulate's office. You can work on this type of visa for three months before you must apply for a residency permit. Portuguese consulates will want to see your passport, a notarized letter from your employer, a health certificate certifying good health, an application form and a birth certificate.
Apply for a residence permit in Portugal. The residence permit is good for five years, can be renewed and must be in good standing to apply for citizenship. Residency permits are granted by the Portuguese Immigration Services an application is available the immigration service website. When applying for a residency permit, bring a Passport and government issued identification, two current photos and, if you have a job, a letter from your employer or proof of sufficient money to live. A residence permit can only be refused for public safety and health. For example, if you carry an infectious disease or have a mental condition deemed dangerous to others.
Learn Portuguese. To become a citizen you must have knowledge of the language and ties to the local community. Get involved in Portuguese groups and through work.
Live in Portugal for at least six years. You can only apply after living in Portugal for six years, proving residency and having an understanding of the Portuguese language. A person married to Portuguese citizen may apply for citizenship after three years.
Apply for Portuguese citizenship, after you've lived in Portugal for at least six years. Apply at a local "Conservatória dos Registos Centrais" office (Central Registry Office). Several offices are located throughout Portugal. Wait times vary by office. Bring documents showing how long you lived in Portugal and the residency visa.