Do I need a visa?

For any category of entry (including as a visitor), you must have a visa if you:
are a national of one of the countries listed in the visa and transit visa nationals page on this website
are stateless (you do not have a nationality)
hold a non-national travel document (a travel document which does not give you the nationality or citizenship of the country that issued it), or
hold a passport issued by an authority that is not recognised in the UK.
If you are a national of one of the countries not listed in the visa and transit visa nationals page on this website, you will generally need a visa if you plan to be in the UK for more than 6 months (there are exceptions to this, so you must check whether your category of visit automatically requires an entry clearance application, e.g. for marriage / civil partnership). A visa will automatically be required if you are applying under PBS Tier 1, Tier 2, Tier 4 and Tier 5 Youth Mobility. If you are not applying under PBS Tier 1, 2, 4 or Tier 5 Youth Mobility or to stay in the UK for more than 6 months (for example, as a visitor), you can apply for entry on arrival. You will still need to meet the requirements of the Immigration rules. You may, however, apply for entry clearance before you travel, if you wish. The relevant fee will need to be paid and your biometrics submitted.
Unlike some countries it is not possible to apply for a UK visa on arrival. Please ensure that you check whether your category of entry requires you to hold a visa before arrival in the United Kingdom (for example, visitor, employment under the Points Based System, study for more than 6 months, entry as a dependant). Failure to hold a mandatory visa can be a costly error and can result in an automatic refusal of entry.