GB — United Kingdom

The United Kingdom consists of England, Scotland, Wales, and Northern Ireland. London, the capital, is one of the world's leading financial and cultural centers. The UK was a member of the EU until Brexit in 2020. The Pound Sterling (GBP) is the world's oldest currency still in use and one of the most traded. For developers, the GB country code maps to the en-GB locale — the second most important English locale after en-US. Note: the ISO 3166-1 code is GB (not UK), but the ccTLD is .uk (not .gb) — this mismatch is a well-known inconsistency. The +44 dialing code serves the UK. Post-Brexit regulatory divergence from the EU (UK GDPR, separate data adequacy) creates compliance complexity. British date formatting (DD/MM/YYYY) differs from American (MM/DD/YYYY), a common source of parsing errors. UK postcodes follow a complex alphanumeric pattern. The National Insurance Number has a specific format. London's fintech ecosystem is among the world's largest, making GBP and en-GB handling critical for financial applications.