Georg Heinrich Sieveking (1 January 1751 in Hamburg, Germany – 25 January 1799 in Hamburg, Germany) was a German merchant and follower of the Enlightenment. Together with his friend and business partner, Caspar Voght, he led one of the largest trading firms in the Hanseatic League during the second half of the 18th century. On 14 July 1790, the first anniversary of the Storming of the Bastille, a freedom celebration organized by Sieveking occurred in Harvestehude, a neighborhood of Hamburg, which received attention far beyond the city. In 1796, a few years before his death, Sieveking succeeded in abolishing the 1793 Hamburg-imposed Embargoes against Paris.
His father's side of the family came from Westphalia, and his grandfather was Ahasver Hinrich (1668–1729) the First, who entered the merchant's trade by founding a business that specialised in trading linen in Versmold. His son Peter Niclaes (1718–1763) followed him in the cloth trade, but went to Hamburg, where he became a citizen in 1747. Only 2 years later he married Catharina Margaretha Büsch, the daughter of a wine merchant who had come to Hamburg from Lüneburg, whose brother Georg Heinrich Büsch had risen to become a Senator of Hamburg. Her first son, born in 1751, was named after him. In accordance with family tradition, he was designated to enter the merchant business, which actually also suited him due to his mathematical talent. Together with his brother Heinrich Christian Sieveking, who was a year younger, he was taught by a private tutor, until both were sent to hear the mathematics lectures of Johann Georg Büsch at the Hamburg commercial academy in 1764.
On 1 August 1766 Sieveking joined the firm of the Hamburg Senator Voght as an apprentice. During his apprentice period he proved himself so diligent that Voght granted him a stake in the firm in 1771, alongside his own son, Caspar. After the Senator's death in 1781, they both continued the business of the firm together, at first under the name "Caspar Voght & Co.", then, after 1788, as "Voght und Sieveking". By Sieveking's 40th birthday on 28 January 1791, Voght had granted him a third of all profits, later he granted him one half. On 1 July 1793, Caspar Voght transferred all activitied to Sieveking, apart from the trade with America, and dedicated himself to other pursuits.