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

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. The Lugii or Lygii had earlier Celtic 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). It is possible that the city of Legnica (Liegnitz) in Silesia was named for Lug, Ligo.

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