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, translated as Baron, not a first or middle name. Before 1919 preceding the first name, former titles are with people alive after 1919 dependent parts of the surname, thus preceding the main surname and not to be translated. The female forms are Freifrau and Freiin.