Under the Portuguese Nationality Law number 37/81, citizenship is based on the principle of ius sanguinis, and can be acquired through descent, marriage or naturalisation. In terms of naturalisation, foreigners can be naturalised in Portugal after proving at least six years of physical residency and pass a Portuguese language test.
Portugal also offers an alternative way to obtain citizenship through its residency by investment program also known as the Portuguese Golden Visa. Under this program an applicant is granted citizenship after a six-year period of residency and upon fulfilling other minor requirements.
Under Portuguese law dual citizenship is allowed without any special conditions and there are no requirements in relation to the renunciation of original citizenship. This means that Portuguese citizens holding second citizenship do not lose Portuguese citizenship, and similarly those acquiring Portuguese citizenship are not required to renounce their original citizenship.