The Guelph Treasure (German: Welfenschatz) is the collection of medieval ecclesiastical art originally housed at Brunswick Cathedral in Braunschweig, Germany. Most of the objects were removed from the cathedral in the 17th century and dispersed in the 1930s.
The Treasure takes its name from the princely House of Guelph of Brunswick-Lüneburg.
The Guelph Treasure passed from Brunswick Cathedral into the hands of John Frederick, Duke of Brunswick-Lüneburg, in 1671, and remained in the Court Chapel at Hanover until 1803.
In 1929 Ernest Augustus, Duke of Brunswick, sold 82 items to a consortium of Frankfurt art dealers Saemy Rosenberg, Isaak Rosenbaum, Julius Falk, Arthur Goldschmidt and Zacharias Hackenbroch. Items from the Treasure were exhibited in the United States in 1930–31. Cleveland Museum of Art purchased nine pieces and more were sold to other museums and private collectors.
In 1934 the remaining 40 pieces of the collection, which had been retained by several German-Jewish art dealers from Frankfurt, were purchased for 4.25 million Reichsmarks via Wilhelm Stuckart by the Prussian State under its Prime Minister Hermann Göring and displayed in Berlin.
The Berlin portion of the Guelph Treasure is now exhibited at the Bode Museum in Berlin.
In 2008 a case for restitution was lodged in Germany by the heirs of the Jewish art dealers over the pieces sold in 1934. In March 2014 the Limbach Commission, an Advisory body to the German government, concluded that the treasure should not be handed over as the case did not meet the criteria defining a forced sale due to Nazi persecution.
However, in February 2015, the heirs to the Jewish art dealers sued Germany and the Bode Museum in the United States District Court for the District of Columbia in order to recover the treasure. A few days before Germany declared the collection for a national cultural treasure, meaning the art pieces can no longer leave the country without the explicit permission of the country's culture minister. It is unclear if the German Culture Minister Monika Grütters was aware of the US lawsuit at the time of the announcement.