Kulm law, Culm law or Chełmno Law (German: Kulmer Recht; Latin: Jus Culmense vetus; Polish: Prawo chełmińskie) was a legal constitution for a municipal form of government used in several Central European cities during the Middle Ages.

It was initiated on 28 December 1233 in the Monastic State of the Teutonic Knights by Hochmeister Hermann von Salza and Hermann Balk when the towns of Thorn (Toruń) and Chełmno (Kulm) received German town law, in particular as a modification of Magdeburg rights. Named after the town it was signed in, the original document (Kulmer Handfeste) was lost in 1244 when the town hall burned due to an attack by Swantopolk II, Duke of Pomerania. The renewed charter of 1 October 1251 was based on a copy in Thorn, but the rights were reduced.

This type of law was mostly granted by the Teutonic Order to cities within their monastic state, but also adopted by cities elsewhere, mainly in the neighboring independent Duchy of Masovia. In addition, the Kulm law was expanded, independently from the Knights, to a larger set of laws called Alter Kulm.

Cities located under Kulm law include: