Fermat's Last Theorem in Lean

Mon, 07 Sep 2026 08:00:00 +0100

Fermat’s Last Theorem has been formally verified! Anthropic translated the proof into Lean, and the machine checked it. The code is on GitHub.

1991

I feel peripherally connected to this result. In 1991 at the International School of Geneva, I wrote my International Baccalaureate extended essay on Fermat’s Last Theorem. At that time nobody had proved it. It had been open for 350 years. Andrew Wiles announced his proof two years later, in 1993. It took another two years and a repaired gap before it was accepted.

Lean on ZeroSharp

Fermat's Last Theorem in Lean

1991