Err (French pronunciation: [ɛʁ] ⓘ; Catalan: Er, locally [ˈer(t)]) is a commune in the Pyrénées-Orientales department in southern France.

The onomastics of the town name, first attested as Ezerre in 839 AD amongst many later forms, is ultimately mysterious.

Linguists generally agree it dates before the dominance of Celtic languages and Latin in ancient Gaul (a dominant hypothesis being a Basque-related Pre-Indo-European name; also see Old European hydronymy).

Err is located in the canton of Les Pyrénées catalanes and in the arrondissement of Prades.

The commune contains the winter sports resort of Err-Puigmal, on the Puigmal mountain.