Łan [wan] (in English lan; in Latin laneus, in German Lahn), is an old unit of field measurement used in Poland. Since the 13th century, its value has varied from one location to another. A greater łan (also Franconian, King's, Old Polish) consisted of 43.2 morgs = 23 to 28 hectares. A lesser łan (Chełmno łan) was 30 morg ≈ 17,955 hectare.
The term derives from German Lehen, "fee" (feudal land tenure). The term łan was also used to indicate an average size of a peasant's tenured farm. Łan was further subdivided into zagony ("belts") and further into skiby ("slices").
In medieval times the size of a łan was anywhere between 3 and 50 hectares, but from the 13th century to 1857 in Great Lesser Poland (with Podkarpacie), the Franconian Łan was consistently used.