Duke Francis Julius of Sachsen-Lauenburg (13 September 1584 in Ratzeburg – 8 October 1634 in Vienna) was a prince of Saxe-Lauenburg.
He acknowledged his brother as the ruling Duke and in return he received the Anker Manor as a residence and an annual pension of 2500 thalers.
Julius Francis served as a chamberlain at the imperial court in Vienna and was entrusted with several diplomatic missions by Emperor Ferdinand II.
Francis Julius also initiated, on behalf of his family, a case before the Aulic Council against the city of Hamburg, about the ownership of the district and castle of Ritzebüttel (today's Cuxhaven).
On 14 May 1620, Francis Julius married Agnes (1592–1629), the daughter of Frederick I, Duke of Württemberg.