I'm now second guessing whether the tag is needed, since we already have jews. (While Ashkenazim are the largest population of Jews, especially in English-speaking countries, they are not the only ones.)
From the ISOGG Wiki:
Examples of endogamous groups include Jews, Polynesians, Low German Mennonites, the Amish, Acadians or Cajuns (French settlers in what is now Nova Scotia, Canada), French Canadians, people from many Arab countries, people from Newfoundland and people from many islands. Endogamy is also a problem in early Colonial American populations.