Jacob Benjamin Wegner (21 February 1795 – 22 May 1864) was a German-born Norwegian industrialist and landowner. He was the co-owner and Director General of Blaafarveværket, Norway's leading industrial enterprise with around 2,000 employees, from 1823 to 1849, and is noted both as a pioneering industrialist as well as a social reformer who introduced a range of benefits for his workers. He was also the owner of Frogner Manor, the main owner of Hafslund Manor and a co-owner of the Hassel Ironworks. He was the consul general to Norway of Hamburg, Lübeck and Bremen, at the time sovereign city states, and of the Kingdom of Portugal. He was married to Henriette Seyler (1805–75), a member of the Berenberg-Gossler-Seyler banking dynasty of Hamburg.
Jacob Benjamin Wegner was born in Königsberg in East Prussia into a shipping family. In 1821 he moved to Berlin to take a position in the merchant house of Gebrüder Benecke. In 1822, Wegner bought Modums Blaafarveværk together with an investment group. The prime investor was merchant banker, Wilhelm Christian Benecke (1779–1860), who was head of Gebrüder Benecke.
Modums Blaafarveværk became the world's leading producer of cobalt pigment, and Wegner was Director General and co-owner of the company from 1822 to 1849. In 1849 Modums Blaafarveværket went bankrupt and came under new ownership.
Wegner was also consul general for the northern German city-states of Hamburg, Lübeck and Bremen, as well as the Kingdom of Portugal. In 1836, he bought Frogner Manor, where Frogner Park is found today.
Wegner was married in 1824 to Henriette Seyler (1805–1875) from Blankenese, a member of the Berenberg-Gossler-Seyler banking dynasty. She was the daughter of banker Ludwig Erdwin Seyler (1758–1836), co-owner of Joh. Berenberg, Gossler & Co., and Anna Henriette Gossler (1771–1836). Henriette Seyler was the granddaughter of Swiss-born merchant turned theatre director Abel Seyler and Sophie Elisabeth Andreae on her father's side and Hamburg banker Johann Hinrich Gossler and Elisabeth Berenberg on her mother's side. Through her paternal grandfather, she was also descended from the Burckhardt, Merian and Faesch patrician families of Basel. Benjamin Wegner's brothers-in-law were banker Gerhard von Hosstrup and ship broker Ernst Friedrich Pinckernelle. Henriette Seyler was the niece of Hamburg senator and banker Johann Heinrich Gossler II and the cousin of Hamburg First Mayor Hermann Gossler (1802–1877).
Wegner and Seyler had four sons and two daughters.
- Johann Ludwig Wegner (b. 1830) was a judge (byfogd), and married Blanca Bretteville, a daughter of Prime Minister Christian Zetlitz Bretteville.
- Heinrich Benjamin Wegner (b. 1833) was a timber merchant and married Henriette Vibe, a daughter of classical philologist Ludvig Vibe.
- Egmont Wegner (b. 1835) died as a child.
- Elisabeth Sophie Dorothea Henriette Wegner (b. 1838) married colonel and aide-de-camp to king Charles, Hans Jacob Nørregaard.
- Anna Henriette Wegner (b. 1841) married theologian Bernhard Pauss, the owner of Nissens Pigeskole (Nissen's Girls School)
- George Wegner (b. 1847) was a Supreme Court advocate and unmarried.
- Steinsvik, Tone Sinding (2000) The Norwegian Cobalt Mines and the Cobalt Works (Stiftelsen Modums Blaafarvevaerk) ISBN 978-82-90734-22-5