Louis De Geer (Liège, 17 November 1587 – Amsterdam, 19 June 1652) was a Walloon/Dutch merchant and industrialist. He is considered the father of Swedish industry for introducing Walloon blast furnaces in Sweden. He produced cannons for the German protestant movement, but also for the Dutch admirals and the Dutch East India Company and the Dutch West India Company.
De Geer was born in Liège/Luik in what today is considered Belgium. He was a brother-in-law of the famous Dutch author P.C. Hooft. In those days Liège was already famous for its iron ore. He set up as a coppersmith in Rouen and in 1611 eventually reached Dordrecht. Having earned a fortune as a banker and industrialist he moved to Amsterdam in 1615. Owing to his extensive travels he received a good education in business.
With the outbreak of the Thirty Years War the demand for weapons increased enormously. In 1618 De Geer delivered weapons to Gustavus Adolphus of Sweden, the Swedish king. Impressed by his business instincts the Swedish Crown allowed him to lease estates near Finspång, Östergötland in eastern Sweden proper. Before long, De Geer had established a formidable workshop industry there. In 1623 he was active in a Swedish trading company.
The Swedish Crown continued to support him and De Geer received the monopoly on the copper and iron trade. De Geer, who adopted Sweden as his second mother country, immigrated to Sweden in 1627. He hoped to evade toll in de Sont. In 1634 he bought het Huis met de Hoofden on the Keizersgracht in Amsterdam. His wife died after the birth of their sixteenth child.
In 1640 De Geer travelled again to Sweden and was ennobled. In his new status he was able to buy 3/4 of the leased farmlands. His house in Stockholm is today the Dutch embassy in Sweden.
Working for Axel Oxenstierna he went to Amsterdam to support the war against Denmark. In 1644, at the start of the Torstenson War against Denmark, he singlehandedly equipped an armada of ships to sail against Denmark. This fleet contained a complete marine, 32 ships with sailors, weaponry and officers. The Swedes were able to conquer Fehmarn in Denmark, thanks to this aid. De Geer is also considered responsible for the Swedish Africa Company. When he founded this company a riot started in Amsterdam in 1649. His family also provided shelter to pacifist and humanist Comenius in his home in Amsterdam. He died in 1662 after falling ill during another voyage to Sweden. He returned to Amsterdam and died there.