---
id: "2016-03-15-alphago-lee-sedol"
url: "https://postcutoff.com/e/2016-03-15-alphago-lee-sedol/"
as_of: "2026-11-13T13:49:00+01:00"
date: "2016-03-15"
date_precision: day
category: milestone
importance: 5
confidence: high
status: [Confirmed]
sources: 3
editor: human editor
human_review: null
version: "2026-10-04"
---

As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2016-03-15-alphago-lee-sedol/

# AlphaGo defeats Lee Sedol 4–1 at Go

DeepMind's AlphaGo beat 18-time world champion Lee Sedol 4–1 in Seoul, a milestone many experts had expected to be a decade away.

## Key facts
- Match played 9–15 March 2016 in Seoul
- Result: AlphaGo 4, Lee Sedol 1
- Combined deep policy/value networks with Monte Carlo tree search
- Nature paper published 27 January 2016 (after beating Fan Hui 5–0 in Oct 2015)
- Move 37 in game 2 became famous for its creativity

## What happened

AlphaGo won the five-game match, with Lee Sedol's only win coming in game 4.

## Why it matters

A watershed for deep reinforcement learning and a 'Sputnik moment' that spurred massive AI investment, particularly in China.

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): in its training data
- Claude Opus 5.5 (training cutoff June 2026): in its training data
- Gemini 4 Hydrogen (training cutoff March 2026): in its training data
- Grok 4.7 (training cutoff May 2026): in its training data

## Sources

1. [Mastering the game of Go with deep neural networks and tree search (Nature, DOI)](https://doi.org/10.1038/nature16961) (doi.org, paper)
2. [Google DeepMind: AlphaGo](https://deepmind.google/research/breakthroughs/alphago/) (deepmind.google, official)
3. [Wikipedia: AlphaGo versus Lee Sedol](https://en.wikipedia.org/wiki/AlphaGo_versus_Lee_Sedol) (en.wikipedia.org, discussion)

## Changes

- 2026-09-29 (filed): Created

## Related

- 2017-12-05: [AlphaGo Zero and AlphaZero master games through pure self-play](https://postcutoff.com/e/2017-12-05-alphazero/index.md)
- 2013-12-19: [DeepMind's DQN learns to play Atari games from pixels](https://postcutoff.com/e/2013-12-19-dqn-atari/index.md)
- 1997-05-11: [IBM Deep Blue defeats world chess champion Garry Kasparov](https://postcutoff.com/e/1997-05-11-deep-blue-kasparov/index.md)