C aspar Callerström is a Swedish investor and a partner at the venture capital firm, EQT Ventures. He has been a key figure in the European technology and investment scene for many years. His wealth is primarily derived from his successful investments in high-growth technology companies, most notably his early and significant investment in the fintech giant Klarna.

As a partner at General Atlantic before joining EQT, Callerström led the firm's investment in Klarna, the Swedish 'Buy Now, Pay Later' (BNPL) company. He sat on Klarna's board for many years, helping to guide it from a European startup into a global fintech powerhouse with a multi-billion dollar valuation. This single investment was immensely successful and is the main source of his fortune. At EQT Ventures, he continues to invest in and mentor the next generation of European technology entrepreneurs.