The legal status of being a recognised citizen of two countries simultaneously. Permitted by most CBI-issuing states and by the majority of major Western jurisdictions, but explicitly prohibited by some.
Dual citizenship — sometimes "multiple citizenship" when more than two are held — is the legal recognition of an individual's citizenship in more than one state at the same time. The acquiring state and the prior state of citizenship must each independently permit it.
All Caribbean CBI states permit dual citizenship. Malta, Portugal, and most EU member states permit it. The United Kingdom, the United States, Canada, and Australia permit it.
Notable jurisdictions that restrict or prohibit dual citizenship include China, India (which offers OCI status instead), Japan (post-22 deadline), Singapore, Indonesia, and Saudi Arabia. Applicants from restricting states should consult a domestic lawyer before pursuing a second citizenship.