The Nikkei 225’s largest one-day percentage fall was 14.90%, recorded on October 20, 1987.
The decline came immediately after the global Black Monday shock of October 19, when markets around the world plunged. Tokyo trading reflected the international panic and the Nikkei suffered its steepest percentage loss in its history.
The Nikkei later experienced a different, prolonged collapse after Japan’s late-1980s asset-price bubble burst. The index reached an all-time closing high of 38,915.87 on December 29, 1989, before falling for many years.
This distinction matters because the 1987 one-day record and the post-1989 Japanese market decline are related but not identical episodes. The Nikkei is a price-weighted index of 225 major Japanese companies listed on the Tokyo Stock Exchange.