Sebastian Siemiatkowski
Stockholm School of Economics · Klarna
His Thesis Idea Was Rejected at a Competition — Then Became Worth $45 Billion
12 March 2026
Sebastian Siemiatkowski presented the idea for Klarna at the Stockholm School of Economics' annual entrepreneurship competition in 2005 — and finished last. The judges didn't think "buy now, pay later" was a viable business.
Ignoring the Judges
Undeterred, Siemiatkowski co-founded Klarna with Niklas Adalberth and Victor Jacobsson. Their product let online shoppers pay after delivery — reducing friction and increasing conversion rates for merchants.
European Expansion
Klarna expanded across Europe, particularly thriving in Germany and the Nordics where consumers were uncomfortable paying upfront online. The company processed billions in transactions and became profitable.
$45 Billion Fintech Giant
At its peak in 2021, Klarna was valued at $45.6 billion, making it Europe's most valuable private fintech. Despite a valuation correction in 2022, Klarna filed for a US IPO in 2024. Siemiatkowski's story proves that expert consensus can be wrong — sometimes finishing last at a competition is the beginning, not the end.
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