The Russell 1000 Index is a U.S. stock market index that tracks the largest 1,000 stocks in the Russell 3000 Index, which represent about 93% of the total market capitalization of that index. The index is market cap weighted, meaning larger companies have a greater influence on the index than smaller companies. As of 31 December 2025, the stocks of the Russell 1000 Index had a weighted average market capitalization of $1.322 trillion and a median market capitalization of $16.5 billion. As of 8 May 2020, components ranged in market capitalization from $1.8 billion to $1.4 trillion. The index, which was launched on January 1, 1984, is maintained by FTSE Russell, a subsidiary of the United Kingdom-based London Stock Exchange Group. The ticker symbol is typically RUI, .RUI or ^RUI. There are several exchange-traded funds and mutual funds that track the index. Wikipedia