TheUerdingen Line (German:Ürdinger Linie, Uerdinger Linie,Dutch:Uerdinger linie; named afterUerdingen byGeorg Wenker) is theisogloss withinWest Germanic languages that separates dialects which preserve the-k sound in the first person singular pronoun word "ik" (north of the line) from dialects in which the word-final-k has changed to word final-ch in the word "ich" (IPA[ç]) (south of the line). This sound shift is the one that progressed the farthest north among the consonant shifts that characterize High German and Middle German dialects. The line passes throughBelgium, theNetherlands, andGermany.^[1]

North of the lineLow German andDutch are spoken. South of the lineCentral German is spoken. In the area between the Uerdingen line and theBenrath line to its south, which includes parts of Belgium and the Netherlands, the Germanic dialectLimburgish is spoken. Especially in eastern Germany, the regional languages have been largely replaced by standardGerman since the 20th century.

The western end of the Uerdingen line is atBierbeek, southwest ofLeuven,Flemish Brabant, Belgium. From there, it runs in northeastern direction, north ofHasselt andWeert, Netherlands, from where it goes straight east. It passes south ofVenlo to cross into Germany'sRhineland. It passes throughKempen andKrefeld-Hüls, and crosses theRhine between Krefeld-Uerdingen andDuisburg-Mündelheim. From there, the isogloss passes south ofMülheim an der Ruhr-Saarn, andEssen-Kettwig, where it turns southeast. It continues pastWuppertal-Elberfeld,Gummersbach andBergneustadt. Further east, it forms the border of theSauerland (to its north) and theSiegerland (to its south). It passes north ofKassel, south ofMagdeburg and north ofWittenberg. In southernBrandenburg in eastern Germany, the isogloss runs byHalbe,Hermsdorf,Freidorf andStaakow.

• High German consonant shift
• Benrath line
• Speyer line
• Weißwurstäquator
• Joret line