Which country has the calling code 011?

011 is not a country code, it is the international access prefix for calls from North America (US, Canada, etc.). International numbers should be written with a plus sign before the country code: for example, +44 for the UK, +61 for Australia, or +211 for South Sudan. The plus sign means "insert your international access prefix here"; different countries use different prefixes, such as 011, 00, 0011, or 8•10.