Sundbyøster (Danish pronunciation: [sɔnpyˈøstɐ]) is one of the 15 administrative, statistical, and tax city districts (bydele) comprising the municipality of Copenhagen, Denmark. It lies on the southeast border of the municipality on the island of Amager. It covers an area of 8.60 km2, has a population of 48,673 and a population density of 5,658 per km2, which makes it the most populated district in Copenhagen. Neighboring city districts are as follows: