Lucas Watzenrode (also, in German, Lukas; in Polish, Łukasz)(1400, in Thorn, Ermland – 1462, in Thorn) was the maternal grandfather of Nicolaus Copernicus.

Lucas Watzenrode the Elder was registered in the Thorn citizen registry book (Thorner Bürgerbuch) as landowner, businessmen, judge, councilman, etc., living at Seglergasse in Thorn. In 1436, he married Katharina von Rüdiger. In 1448, he and other Thorn burghers are registered as having been summoned to the court at Limburg.

Lucas and his wife Katharina had a daughter, Barbara, who married Nicolas Kopernik. Barbara's sister Christina married Tideman von Allen. Both sisters married in Thorn.

Lucas Watzenrode the Elder's grandson became known as Nicolaus Copernicus. Copernicus had an uncle, his mother's brother, also named Lucas Watzenrode (known as Lucas Watzenrode the Younger), who as Bishop of Ermland strongly supported the independence of Ermland and helped raise Nicolaus and his brother Andreas after their father's death.

Christina and Tideman's daughter Cordula von Allen married Reinhold Feldstedt, who was born in 1468 in Danzig and died in 1529 in Danzig. Their daughter Katharina Feldstedt married Herman Giese, born in 1523 in Danzig. A descendant was Tiedemann Giese, a famous bishop of Ermland.

• Bishops of Warmia
• Nicolaus Copernicus

• Library Danzig, J. Kretzmer, Liber de episcopatu et episcopi Varmiensis ex vetusto Chronico Bibliotheca Heilsbergensis, 1593.
• Christoph Hartknoch, Preussische Kirchen-Historia, Frankfurt am Main, 1668.
• M.G. Centner, Geehrte und Gelehrte Thorner, Thorn, 1763.
• A. Semrau, "Katalog der Geschlechter der Schöffenbank und des Ratsstuhles in der Altstadt Thorn 1233-1602", in: Mitteilungen des Copernicus-Vereins für Wissenschaft und Kunst zu Thorn 46, 1938.
• Wojciech Iwanczak, "Lucas Watzenrode", in Biographisch-Bibliographisches Kirchenlexikon, Bautz Verlag [1].
• Poczet biskupów warmińskich, Olsztyn, 1998.