The Lugii, Lygii or Ligii (also Lygians, Lugians) were a tribe of likely Celtic or Germanic origin living in procimity of Silesia (modern Poland) north of the Sudetes mountains between Oder and Vistula rivers.

The Lugii or Lygii had earlier Celtic La Tene elements and were actually recorded as a part of the Vandals in Magna Germania, which included territory of later Silesia (named for the Silingi -Vandals). Ptolemy records the continuation of these Germanic tribes. It is possible that the city of Legnica (Liegnitz) in Silesia was named for Lug, Ligo.

The connection between the Lugii and the Slavs is controversial. Some recent authors connect them with Slavs, some with Germans, and still others claim that the Lugii were a compound tribe, or confederation of tribes of different ethnicity.

Lugii are probably connected to Lingones, a Celtic tribe in Transalpine Gaul (modern France) and Cisalpine Gaul (northern Italy).