Karl Walter Friedensburg (6 March 1855 in Hamburg – 19 February 1938 in Wernigerode) was a German historian and archivist.
In 1901, he was appointed director of the Staatsarchiv Stettin (National Archives in Stettin), and in 1913 succeeded Georg Winter (1856–1912) as director of the State Archives of Magdeburg.
He entered into retirement in 1923, relocating to Wernigerode during the following year.
From 1913, he was a member of the Historischen Kommission für die Provinz Sachsen und für Anhalt (Historical Commission for the Province of Saxony and for Anhalt), serving as its chairman in 1922–23.
Friedensburg's prime area of research involved the history of the Reformation.