Richard, 6th Prince of Sayn-Wittgenstein-Berleburg (Richard Casimir Karl August Robert Konstantin; 29 October 1934 – 13 March 2017)^[1] was the head of the House of Sayn-Wittgenstein-Berleburg and husband of Princess Benedikte of Denmark.

Richard Casimir Karl August Robert Konstantin was the eldest son and child of Gustav Albrecht, 5th Prince of Sayn-Wittgenstein-Berleburg, a highly decorated German army officer declared missing in 1944 yet only legally declared dead in 1969, and his wife, Margareta Fouché d'Otrante, a descendant of Napoleonic statesman Joseph Fouché, Duke d'Otrante.^{[citation needed]}

Richard was raised in Sweden with his maternal grandfather, the Duke of Otranto, at Elghammar Castle. He attended the boarding schools Viggbyholm and Sigtuna.

Having studied arboreal science at Munich University, Prince Richard obtained his forestry diploma at the University of Göttingen in Lower Saxony. He took post-graduate training as Forstreferendar, obtaining a degree as Assessor des Forstdienstes after passing the second-level examination at the North Rhine Westphalian State Forestry Service.^[2]

Richard married Princess Benedikte of Denmark at Fredensborg Palace Church on 3 February 1968. She is the second daughter of Frederik IX of Denmark and Ingrid of Sweden, younger sister of Margrethe II of Denmark and elder sister of Queen Anne-Marie of Greece.^[2] The couple lived at Berleburg Castle. Pursuant to the marriage contract, in Denmark Richard and his children by Princess Benedikte were to be attributed the style of Highness, rather than the unknown Durchlaucht ("Serene Highness") to which all Sayn-Wittgenstein princes were historically entitled in Germany.^[3]

While the couple were raising their family Princess Benedikte reduced her royal engagements in Denmark, where she spent only about a quarter of her time.^[3]

Prince Richard engaged in several conservation programmes, while responsible for managing his family's extensive lands in Germany.^[3] He launched a project to re-introduce European bison to the native continent on part of his 32,000 acre estate in North Rhine-Westphalia, credited as a success by Rewilding Europe as part of a larger effort to restore depleted animals across Europe.^[7]

In July 2003, he underwent surgery for treatment of prostate cancer; previously, he had undergone treatment for skin cancer.^[8]

Prince Richard died suddenly on 13 March 2017 at the castle of Berleburg in Germany.^[9] He was 82.