Sebastian Siemiatkowski
Born 1981 · Age 44
Swedish entrepreneur; co-founder and long-time CEO of fintech company Klarna. Born to Polish immigrant parents, SSE alumnus, led Klarna from a student project in 2005 to a global BNPL and payments business.
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Life & Career Timeline
Parents moved from Poland to Uppsala (family background)
His parents moved to Uppsala from Poland in the early 1980s (source notes early 1980s).
Born in Sweden
Sebastian Siemiatkowski was born in Sweden; parents had moved from Poland to Uppsala in the early 1980s.
Family acquired first home computer (influential policy)
Sebastian credits Sweden's subsidised computer ownership policy for enabling his family to buy their first computer — a formative influence on his interest in tech.
Parents divorced
Parents divorced when Sebastian was 11; he later recalled this childhood hardship shaped his view on money and ambition.
Attended Katedralskolan, Uppsala (high school)
Attended high school at Katedralskolan in Uppsala (exact start/end years not listed; typical Swedish gymnasium ages).
First job — Burger King (flipping burgers)
Sebastian's first job was flipping burgers at Burger King; he later met co-founder Niklas Adalberth while working there.
Started studies at Stockholm School of Economics
Began higher education at the Stockholm School of Economics (Clay dossier lists enrollment 2000–2007).
Worked in telesales and cold-calling roles
Worked in telesales early in his career, learning sales and customer-facing skills prior to founding Klarna.
Promoted to sales team manager (age 21)
At age 21 he was promoted to manage a sales team — an early management milestone (reported in interviews).
Head of Sales at Djuice Uppsala (sales experience)
Accumulated sales experience including a role as head of sales at Djuice Uppsala; sources say he had ~8 years in sales in total.
Traveled around the world (trip before founding Klarna)
One year before starting Klarna he and co-founder Niklas travelled around the world for half a year without flying — a formative life experience.
Met co-founder Niklas Adalberth (while at Burger King)
Met future co-founder Niklas Adalberth while working at Burger King; relationship later led to founding Klarna together.
Presented Klarna idea at SSE innovators pitch
Klarna was launched as part of a competition at the Stockholm School of Economics; judges initially sceptical but an observer encouraged them to continue.
Co-founded Klarna
Co-founded Klarna with Niklas Adalberth and Victor Jacobsson; started building the company at age 23. Clay dossier cites February 2005 as start.
Completed MSc from Stockholm School of Economics
Graduated from the Stockholm School of Economics with a Master's (sources state graduation in 2007).
First institutional funding: Investment AB Öresund
Klarna received early funding from Investment AB Öresund in 2007, enabling expansion beyond Sweden.
Named to Forbes 30 Under 30 (recognition)
Profiles note inclusion in Forbes' '30 Under 30' list; year not specified in all sources — placed as late 2000s when he was eligible.
Assumed (or consolidated) CEO role at Klarna (by 2010)
Sources note that by 2010 Sebastian had taken on the role of CEO as Klarna scaled — some sources list him as CEO from early days; this marks consolidation of leadership.
Sequoia Capital investment (additional funds raised)
Klarna raised additional funds from Sequoia Capital that accelerated revenue growth (precise year not specified in all sources; placed here based on narrative sequence).
Raised US$155m (General Atlantic & DST Global)
Klarna raised approximately US$155m from General Atlantic and DST Global as it began major scaling.
Merger with SOFORT AG — formed Klarna Group
Klarna merged with SOFORT AG in 2013, creating Klarna Group and strengthening its European payments footprint.
Purchased / renovated family home in central Stockholm (personal milestone)
profile pieces described Sebastian and Nina renovating a central Stockholm property they live in; restoration took several years to complete.
Married Nina (Sundén)
Married Nina, a marketing executive he first met at Stockholm School of Economics; she later helped identify the agency that created Klarna's branding.
Macy's partnership (Klarna's first US foray — exclusive deal)
Klarna signed an exclusive partnership deal with Macy's in the US, marking one of its first major entries into the US market (source mentions the deal but not exact date; placed mid-2010s).
Named to Fortune 40 Under 40 (recognition)
Profiles indicate he was later recognised in Fortune's '40 Under 40' list (year not precisely given in sources — placed mid-2010s).
Began family life — three children (family milestone)
Sebastian and Nina have three children and live in Stockholm; children born across the marriage period (specific birth years not listed).
SSE Business Lab advisory role ends (June 2019 end recorded)
Clay dossier lists advisory term May 2015–June 2019 for SSE Business Lab; end date recorded as June 2019.
Runner-up, Global EY Entrepreneur Of The Year
Recognised as runner-up in the 2015 Global EY Entrepreneur of the Year awards.
Awarded Leader of the Year by Adecco (date cited in profiles)
Named Leader of the Year by Adecco (profile sources state he received this recognition; exact year sometimes grouped with other mid-2010s awards).
European Entrepreneur of the Year by TechTour (recognition)
Received TechTour's European Entrepreneur of the Year award (profile sources list this accolade; year commonly cited as mid-2010s).
Public leadership lessons and interviews (HuffPost CEO Talk)
Featured in CEO interview series discussing leadership, hiring and company culture (HuffPost 'CEO Talk' condensed interview published mid-2010s).
Appointed to SSE Business Lab advisory board
Served as an advisory board member at the Stockholm School of Economics' SSE Business Lab (Clay dossier lists May 2015–June 2019).
Klarna crosses ~1,500 employees (scaling milestone cited)
Company scaled from a small founding team to more than ~1,500 employees (HuffPost noted growth from 3 people to 1,500+).
Klarna named Europe's biggest fintech startup (by some metrics)
By this period Klarna was widely described as Europe's largest fintech startup (based on fundraising and valuation metrics reported around 2019).
Raised US$460m for US expansion
Klarna raised about US$460m in 2019 to consolidate its position and expand into the US market.
Klarna workforce and merchant milestone (reported scale)
By around 2020 various profiles documented Klarna's merchant footprint in the hundreds of thousands and rapid global growth trajectory.
Personal valuation reportedly exceeded US$2bn (pre-40)
Profiles reported Sebastian's personal valuation climbed above US$2bn as Klarna reached peak valuations in the early 2020s.
Klarna valuation reached ~US$31bn (minted as billionaire)
Klarna's valuation increased to roughly US$31bn and Sebastian was reported as becoming a billionaire (multiple sources reference 2021 valuation increases).
SoftBank-led / Vision Fund investment (large funding round)
Klarna received a large investment (~US$639m) led by SoftBank's Vision Fund 2, producing very high valuations reported in the press (sources place this round in the early 2020s).
Reported layoffs magnitude (approx. 700 workers cited in some reports)
Some coverage cited that about 700 employees were affected by the rounds of job cuts; numbers vary by report.
Swedish Financial Sector Union sued Klarna over layoffs
The Swedish Financial Sector Union said it was not consulted and sued Klarna over the layoffs (reported in 2022 coverage).
Net worth estimated at US$3.2bn (profiled valuation)
Profiles (Wikipedia referencing Forbes) reported Sebastian's net worth was estimated at US$3.2 billion in 2022 as Klarna's valuation increased.
Klarna laid off ~10%; CEO posted dismissed employees' names publicly
Klarna laid off about 10% of employees; Sebastian publicly posted a list of recently dismissed employees (including emails), which drew strong criticism.
Public profile pieces & interviews (GQ / Reuters / Bloomberg coverage)
Major media outlets profiled Sebastian and Klarna's approach to payments and scaling in 2023; coverage included in-depth interviews about leadership style.
Klarna global scale milestone (customers, merchants, employees cited)
Profiles cite Klarna having more than ~150 million active customers, partnerships with 500,000+ merchants and 5,000+ employees (figures reported in recent coverage).
Stated Klarna will not increase headcount due to AI capabilities
In December 2024 he publicly stated the company would not increase headcount because 'AI can do all of the jobs that we humans do.'
Forbes coverage / net worth tracking (profile updated)
Forbes listing and profiles on Sebastian and Klarna were updated / referenced in 2025 (source retrieval date May 7, 2025).
No longer a billionaire (net worth fell below US$1bn)
Profiles note that as of 2025 Sebastian is no longer a billionaire after valuation declines at Klarna; exact figure not published — estimated decline from peak.
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