Knut Agathon Wallenberg

Wallenberg was born on 19 May 1853 in Katarina Parish, Stockholm, the son of André Oscar Wallenberg (1816–1886) and his first wife Catharina Wilhelmina Andersson (1826–1855). He was the brother of Oscara (1847–1863), Jacob (1851–1872), and Wilhelm (1855–1910). He also had 14 half-siblings, including Gustaf (1863–1937), Marcus (1864–1943), and Victor (1875–1970).

In 1874 Wallenberg was commissioned as a naval officer and became Acting Sub-Lieutenant (Underlöjtnant) in the Swedish Navy the same year and joined the board of Stockholms Enskilda Bank. In 1876 he went to Georgiis' Banking Institution (Georgiis bankinstitut), and he was appointed lieutenant in the navy in 1876, from which he resigned in 1882. Wallenberg was then employed by the Crédit Lyonnais in Paris from 1877 to 1878. After his father's death, Wallenberg, who has long been involved in the management of Stockholms Enskilda Bank, took over as the CEO. In many respects his father's spiritual heir, the company led by him became one of Sweden's foremost, which mediated the taking up of large government loans and other significant deals. He was also the driving force for many in the economic field, including in the creation of the residential community Saltsjöbaden near Stockholm and the railways connecting these places. From 1883 he belonged to the Stockholm City Council (Stockholms stadsfullmäktige) and from 1890 its Drafting Committee (Beredningsutskottet).

In 1878 he married Alice Olga Constance Nickelsen (1858–1956). The couple adopted Jeanne Nyström (1885–1962), who was then two years old, in 1887 and she was named Nannie Wallenberg. She was born out of wedlock to Jean Karadja Pasha, and thus half-sister to Constantin Karadja.