Mlechha is a derogatory word for foreigners in Hindu scriptures. It was also used for unclean people. Sakas, Hun, Pulinda and many other foreign tribes were referred by this term. Kautilya however has restricted the term for white Huns only who were known for their uncleanliness. Manusmriti has called them Shudra, the same view is subscribed by Panini too. Sometimes it is also called fifth varna in Indian caste system.

Mlechha word is derived from two root words mal-meaning dirt and ichha meaning willingness, hence the word means one who has willingness for dirty things. A great amount of work on mlechha is found in Mahabharata. North west of the Indian subcontinent has also been referred to as Mlechhadesh meaning abode of mlechha.

However all Mlechhas were not treated uniformly and sometimes they were also called Kshatriya if they fulfilled wishes of Brahmins and protected them .Manusmriti endorses that it was an arbitrary system in which foreign tribes were called anything spanning between Kshatriya and Shudra depending upon their domination and relationship with Brahmanas.Many became Brahmin too.