The Nikkei 225 reached 38,957.44 at the peak of Japan's 1989 asset-price bubble.
That record closing level was reached on December 29, 1989. The Nikkei 225 is a price-weighted index of major companies listed on the Tokyo Stock Exchange, so it became the most recognizable measure of the enormous rise and subsequent collapse in Japanese share prices.
Japan's bubble was linked to rapid credit growth, soaring land prices, strong optimism, and aggressive lending. After the Bank of Japan tightened monetary policy, asset prices began to fall. The Nikkei then entered a prolonged decline, while the economy experienced years of weak growth and financial stress.
The 1989 figure is often confused with later recovery milestones or with the broader TOPIX index. The question refers specifically to the Nikkei 225's closing peak, not an intraday value or a different Japanese benchmark.