When Mathieu Flamini hung up his boots in 2019, few could have predicted that the industrious French midfielder — once known for his tireless energy at Arsenal and AC Milan — would go on to become one of the wealthiest former footballers in history. Fast-forward to 2025, and Flamini’s post-football life has taken an astonishing turn. With an estimated net worth of £10 billion, he is now a pioneering figure in sustainable energy — a man whose legacy off the pitch could far outshine his achievements on it.

A Solid, Yet Unspectacular, Football Career

Born in Marseille, Flamini’s footballing journey began with his hometown club before a move to Arsenal in 2004 catapulted him into the Premier League spotlight. Known for his grit, versatility, and relentless work rate, he made 246 appearances across two spells for the Gunners. His time in North London yielded three FA Cups and two Community Shields, and he came agonisingly close to Champions League glory in 2006, when Arsenal fell to Barcelona in the final.

Between his Arsenal stints, Flamini spent five seasons at AC Milan, where he added a Serie A title to his résumé in 2011. He also represented France three times at international level. Though not the most glamorous name of his generation, Flamini earned a reputation as a dependable team player — the kind of midfielder every manager valued for his discipline and drive.

But it’s what Flamini did away from the pitch that would redefine his legacy.

From Tackles to Test Tubes: The Birth of GF Biochemicals

In 2008, shortly after leaving Arsenal for Milan, Flamini quietly co-founded GF Biochemicals with his business partner, Italian economist Pasquale Granata. Their goal was ambitious: to revolutionise the energy sector by finding sustainable alternatives to fossil fuels.

The pair poured millions into research and development, focusing on a substance called levulinic acid, a bio-based compound made from plant waste that could be used to replace petroleum in manufacturing plastics, cosmetics, and pharmaceuticals.

In 2015, their company achieved a historic breakthrough — becoming the first in the world to mass-produce levulinic acid. It was a moment that marked GF Biochemicals as a leader in the green chemistry revolution, and it sent shockwaves through both the scientific and business communities.

By 2025, the company is reportedly valued at £21 billion, and Flamini, who owns a 60% stake, has seen his personal fortune soar past the £10 billion mark — eclipsing even global superstars like Cristiano Ronaldo and Lionel Messi.

Reflecting on his journey, Flamini once joked to Les Echos:

“My teachers must be surprised. Having left for Arsenal at 19, I now speak English as well as French — and I run a biochemistry company!”

The Environmentalist Entrepreneur

Flamini’s passion for sustainability isn’t new. Growing up near the sea in Marseille, he says he became aware of environmental issues from a young age, particularly around ocean pollution. In an interview with Sifted, he shared:

“As a child, I had two passions: football and sustainability.”

For the first five years of GF Biochemicals, he kept the project secret — even from his teammates — uncertain of its direction and wary of being dismissed as just another footballer dabbling in business. Yet his persistence paid off, and today he is one of the leading voices in eco-entrepreneurship.

Flamini has since expanded his vision through Re-Chemistry, a sister company focused on creating sustainable health and wellness solutions. In a humorous social media post from 2025, he reflected on his unlikely transformation:

“The subjects I hated most in school were chemistry and English. Now I’m CEO of Re-Chemistry, creating sustainable solutions for our planet — and I spend 90% of my time speaking in English. It’s funny how the world works.”

Eyeing a Return to Football — This Time as an Owner

Despite his success in business, Flamini hasn’t ruled out a return to football — but not in boots. With a fortune large enough to buy a significant stake in a Premier League club, the 40-year-old has hinted at an interest in owning one of his former teams, Arsenal or Marseille.

Speaking to The Athletic, he said:

“Those clubs have a special place in my heart. In life, it’s all about the right time, right place, right people. Let’s see what the universe brings.”

Such a move would be unprecedented — a former player returning not as a manager or pundit, but as a billionaire owner shaping the club’s future from the boardroom.

Teaming Up with Mesut Özil

Flamini’s entrepreneurial ventures haven’t been limited to green energy. Reuniting with former Arsenal teammate Mesut Özil, he co-founded Unity Performance Lab, a digital health and fitness platform. The project blends scientific wellness insights with elite sports expertise, offering users evidence-based training and recovery tools.

Even with a packed business schedule, Flamini’s energy levels remain unchanged. He describes himself as “hyperactive,” often taking conference calls while walking or running through Hyde Park. “I train at least five times a week,” he told Les Echos. “It helps me disconnect intellectually.”

The discipline and resilience that defined his playing career, he says, have been crucial in business. “In football, you perform under pressure in front of 60,000 people. In business, it’s similar — either you commit 200% or you disappear.”

From Footballer to Visionary

Flamini’s story is one of reinvention and purpose. Where many retired athletes struggle to fill the void left by sport, he has channeled his competitive drive into something far bigger — tackling one of humanity’s greatest challenges: sustainability.

When NME named him one of their People of the Year in 2015, it wasn’t for his goals or trophies, but for his environmental impact — a testament to how far he’s come.

Today, Mathieu Flamini stands as a rare example of an athlete whose greatest victories came after the final whistle. From chasing midfield battles to leading a billion-pound eco-revolution, his journey proves that success isn’t confined to the pitch — and that passion, when paired with purpose, can change the world.