Illegal immigration 非法移民
（重定向自Undocumented alien）
![Border patrol at sea by the U.S. Customs and Border Protection](/Images/godic/202502/18/Office_of_CBP_Air_and_Marine_helicopter_and_boats1531.jpg")
![HMC Vigilant, one of several customs cutters of the UKBA, capable of speeds up to 26 knots departing Portsmouth Naval Base.](/Images/godic/202502/18/HMRC_Vigilant_BB1531.jpg")
![Aerial view of São Paulo, where most illegal immigrants in Brazil live.](/Images/godic/202502/18/Saopaulo_paulista1531.jpg")
![ABVP against Bangladeshi illegal immigrants](/Images/godic/202502/18/Bangladeshi1531.jpg")
Illegal immigration is the migration of people across national borders in a way that violates the immigration laws of the destination country. Some countries have millions of illegal immigrants. Immigration, including illegal immigration, is overwhelmingly upward, from a poorer to a richer country. However, it is also noted that illegal immigrants tend not to be the poorest within the populations they emigrate from.