Ketteler and also Kettler is the name of a German noble family of Westphalia. Goswin Ketteler zu Assen (c. 1400 – c. 1471) divided the property with his younger brother Röttger around 1440. He built a new house on his part of the ground and called himself since then Kettler Neu Assen. He changed the background of his coats from silver to gold - the so-called golden line. The silver line still spells Ketteler and is called the silver line Ketteler Alt Assen.
- Clemens August Freiherr von Ketteler (22 November 1853 – 20 June 1900) was a German career diplomat. He was killed during the Boxer Rebellion, an event which prompted the Eight-Nation Alliance to declare war on China.
- Wilhelm Emmanuel Freiherr von Ketteler (25 December 1811 – 13 July 1877) was a German theologian and politician who served as Bishop of Mainz. His social teachings became influential during the papacy of Leo XIII and his encyclical Rerum novarum.
- Gotthard Kettler, (also Ketteler, German: Gotthard Kettler, Herzog von Kurland; 1517, nearby Anröchte, Kreis Soest – 17 May 1587, Mitau) was the last Master of the Livonian Order and the first Duke of Courland and Semigallia.
- Regarding personal names: Freiherr was a title before 1919, but now is regarded as part of the surname. It is translated as Baron. Before the August 1919 abolition of nobility as a legal class, titles preceded the full name when given (Graf Helmuth James von Moltke). Since 1919, these titles, along with any nobiliary prefix (von, zu, etc.), can be used, but are regarded as a dependent part of the surname, and thus come after any given names (Helmuth James Graf von Moltke). Titles and all dependent parts of surnames are ignored in alphabetical sorting. The feminine forms are Freifrau and Freiin.