These are lists of countries by foreign-born population (immigrants) and lists of countries by number native-born persons living in a foreign country (emigrants).
According to estimates from the UN 2015 report, in 2013, the United States, Germany and Russia had the largest number of immigrants of any country, while Tuvalu and Tokelau had the lowest. In terms of percentage of population the Vatican City and the United Arab Emirates had the highest, while North Korea had the lowest.
UN 2015 report: immigrant population
This is a list of countries by estimated foreign-born population in 2013, defined by the UN as "persons living in a country other than where they were born," as reported by the United Nations Department of Economic and Social Affairs 2015 report Trends in International Migrant Stock: The 2015 Revision. According to the UN these estimates were "based on official statistics on the foreign-born or the foreign population."
UN 2015 report: emigrant population
OECD 2015-2016 Factbook
This is a list of countries by foreign-born population (including those who hold only the citizenship of the country of residence), and foreign population, which the OECD defines as the percentage of population who hold a foreign citizenship (including those born in the country of residence), the OECD Factbook 2015-2016:
UN 2005 report
This is a list of countries by immigrant population, based on the United Nations report World Population Policies 2005.  The total immigrant population was estimated to be 186,579,300. UN member and observer states are ranked.
Western Sahara did not supply data. Western Sahara is a disputed territory in North Africa, mostly administered by Morocco, and claimed by both Morocco and the Sahrawi Arab Democratic Republic. Immigration to the Moroccan-administered region is primarily from other Moroccan regions. The area administered by the Sahrawi Arab Democratic Republic is sparsely populated.)