No. The official TLD – i.e. “Top Level Domain”, is .uk. It differs from the normal ISO 3166 two-character country code, GB, even though most other countries have an identical TLD and ISO two-character code. The TLD .gb is merely reserved to deter shenanigans.

Both .GB and .UK are the country code top-level domains; .GB because that's the official code, and .UK for legacy reasons.

UK is a reserved ISO 3166 code, to prevent complications with DNS TLD assignment.

The .GB TLD is in use, but there are only three known domains. This is one:

  host hermes.dra.hmg.gb
  hermes.dra.hmg.gb has address 146.80.9.16
  hermes.dra.hmg.gb mail is handled by 10 relay.dstl.gov.uk.

There were some mil.gb domains at one point.

Cooler fact, GB and UK are different. UK is GB + Northern Ireland.

Scotland already have .Scot and I think Wales have thier own also. Not sure I've seen a .England though.

.en would seem apt.

.uk is also the UK's though. The country code is explicitly reserved by the UK, and it exists in DNS because they grandfathered in some old system's domains.