The S&P 100 is a stock market index of United States blue chip large-cap stocks maintained by S&P Dow Jones Indices.
The S&P 100 is a subset of the S&P 500 and the S&P 1500, and holds stocks that tend to be the largest and most established companies in the S&P 500. However, the S&P 100 actually includes 101 larger US company stocks due to holding two different share classes of Alphabet Inc.
Constituents of the S&P 100 are selected for sector balance and represent nearly 71% of the market capitalization of the S&P 500 and 61% of the market capitalization of the U.S. equity markets as of December 2024.
Index options on the S&P 100 are traded with the ticker symbol "OEX". Because of the popularity of these options, investors often refer to the index by its ticker symbol.Wikipedia