Japan’s Nikkei 225 reached a closing peak of 38,915.87 on December 29, 1989, before the country’s asset-price bubble collapsed.
The late-1980s Japanese bubble featured rapidly rising land and equity prices, abundant credit, and strong optimism about Japan’s economy. The Nikkei’s 1989 peak became a landmark in financial-market history because the index then entered a prolonged decline.
The Bank of Japan raised interest rates beginning in 1989, and asset prices weakened. The market’s losses continued into the 1990s as falling land values, bad loans, and weaker economic conditions damaged banks and companies. Japan’s experience became known as the Lost Decades.
Some references give slightly different figures because they distinguish between intraday and closing records. The canonical closing peak is 38,915.87, while the index’s intraday high was higher. The question concerns the closing level, not the highest price reached during the trading day.