https://en.wikipedia.org/wiki/District_9

From the plot summary (no spoilers other than the first few minutes of the film):

In 1982, an extraterrestrial mothership arrives and hovers over the South African city of Johannesburg. Inside, an investigation team finds over a million starved insectoid and crustacean-like aliens and the South African government voluntarily relocates the asylum seekers to a refugee camp called District 9. 28 years later, District 9 becomes both a ghetto and a shanty town, and humans come to view the aliens, derogatorily called “prawns,” as filthy, violent animals who bleed resources from them. The Prawns have been systematically reduced to second-class citizens there and have been known to consume canned cat food.