The legal process by which a non-citizen acquires citizenship of a country, typically after a qualifying period of residency and the satisfaction of integration requirements.
Naturalisation is the standard pathway from long-term residency to citizenship. Most jurisdictions require an unbroken period of legal residence (commonly 5–10 years), proof of integration (language test, civic knowledge test, or both), a clean criminal record, and renunciation of prior citizenship in some cases.
In the investment-migration context, naturalisation is the end-state of every RBI / Golden Visa pathway. Portugal's five-year window is the shortest in Western Europe; Malta's 12- or 36-month MEIN route is technically a residency-then-naturalisation programme rather than direct CBI.
Naturalisation is distinct from CBI, which grants citizenship directly without a prior residency period.