Megacap stock

In business and investing, a megacap stock (also mega-cap or mega cap) is a stock whose market capitalization (market cap) is among the very largest. These are stocks of the largest publicly traded companies in the world. The market capitalization of a stock is the total value of the shares outstanding, calculated as (shares outstanding x share price).^[1] Stocks with large market caps, but smaller than megacaps, instead fall within the large-cap segment of the stock market.

There is no official definition of, or full consensus agreement about, the exact market cap cutoff value for a stock to qualify as megacap,^[2][3][4] and it may vary internationally. However, for the 2020s US market, a minimum market cap value of $200 billion is often cited.^{[5][6][7][2][8][9][10]} Index providers, investment funds, and investment managers may have other definitions.

In the US, according to the Financial Industry Regulatory Authority's 2022 investor education materials, the megacap segment is typically (though not officially) defined as stocks with a market cap of at least $200 billion,^[5] which is equivalent to at least $213 billion in 2024 using GDP deflator adjustment.^[11]

Several stock market indices have been created which attempt to measure the megacap segment of the US stock market, and thus implicitly define versions of the megacap segment. Index funds have been created which track some of those indices.

The CRSP US Mega Cap Index (total return ticker symbol: CRSPMET​) "target[s] the top 70% of investable [US] equity market capitalization".^[12] Accordingly, as of March 31, 2026, the Center for Research in Security Prices (CRSP) defined their US megacap segment as companies with market caps greater than $84,668,658,578.56.^[13] As of September 30, 2025, the index contained 179 companies.^[12] The Vanguard Group issues an index ETF (NYSE Arca: MGC) that tracks this index.^[14]

At initial creation circa February 2024, the MSCI USA Mega Cap Select Index consisted of companies in the MSCI USA Index with market caps of at least $200 billion.^[10] As of June 2026, the index's rules constrain it to contain 30 to 50 constituents.^[10] If possible while still complying with that minimum constituents requirement, new additions to the index are required to have a market cap of at least $220 billion.^[10] As of May 29, 2026, the index contained 50 constituents, with market caps ranging from $98.4 billion to $4.84 trillion.^[15]

The Russell Top 200 Index is officially described as "[measuring] the performance of the mega cap segment of the US equity market".^[16] As of April 30, 2026, the Russell Top 200 contained 198 constituents, with market caps ranging from $62.1 billion to $4.85 trillion.^[17] The narrower Russell Top 50 Mega Cap Index consists of the 50 largest companies in the Russell 3000 at the time of index reconstitution.^[18] As of April 30, 2026, the Russell Top 50 Mega Cap Index contained 51 constituents, with market caps ranging from $216.6 billion to $4.85 trillion.^[17]

A 2025 article by S&P Dow Jones Indices describes its own S&P 100, S&P 500 Top 50 (ticker: SP5T5), S&P 500 Top 20 (ticker: SP5T2), and S&P 500 Top 10 (ticker: SP5T1) indices as "mega-cap indices".^[19] As of May 29, 2026, the S&P 100 index's methodology required a minimum market cap of $22.7 billion, and the index's 101 constituents had actual market caps ranging from $55.1 billion to $5.13 trillion.^[20] As of May 29, 2026, the S&P 500 Top 50 Index contained 51 constituents, with market caps ranging from $92.3 billion to $5.13 trillion.^[21] Invesco issues an index ETF (NYSE Arca: XLG) that tracks the S&P 500 Top 50 Index.^[22] As of May 29, 2026, the S&P 500 Top 20 Index contained 21 constituents, with market caps ranging from $316 billion to $5.13 trillion.^[23] The S&P 500 Top 20 Select Index (ticker: SPXT2SUP) is a capped variant of the S&P 500 Top 20 Index, limiting any single company's weight in the index to a maximum of 22.5%, and limiting companies with weights above 4.5% to collectively constitute at most 48% of the index's weight.^[24] BlackRock iShares issues an index ETF (NYSE Arca: TOPT) that tracks the S&P 500 Top 20 Select Index.^[25]

A few actively managed investment funds have been created which target the megacap segment of the US stock market. They explicitly give their own definitions of the megacap segment when explaining their investment strategies.

The Fidelity Mega Cap Stock Fund mutual fund (ticker symbol: FGRTX) defines megacaps as companies "whose market capitalization is similar to the market capitalization of companies in the Russell Top 200 Index or the S&P 100 Index".^[26] As of December 31, 2025, the fund had 116 holdings.^[27]

The Principal US Mega-Cap ETF (Nasdaq: USMC) defines megacaps as companies "with market capitalizations in the top 50th percentile of the S&P 500 Index".^[28] As of September 30, 2025, such companies had market caps ranging from $149.6 billion to $4.6 trillion.^[28] As of June 30, 2025, the fund had 27 holdings.^[29]

The origin and first recorded use of the term megacap (or any of its various spellings), in relation to stock capitalization, is unclear. It dates back to at least 1997,^[30] if not earlier.

The S&P 100 was launched on June 15, 1983.^[31] The Russell Top 200 Index was launched on September 1, 1992.^[16] The Fidelity Mega Cap Stock Fund's inception was on December 28, 1998.^[32]

The Russell Top 50 Mega Cap Index was launched on January 1, 2005.^[18] Also in 2005, investment advisory executive Richard Imperiale noted that some investors were classifying "the top 10 percent of companies by market cap" into a mega cap segment of the stock market.^[33]

In 2009, the third edition of Stock Investing For Dummies defined mega caps (and ultra caps) as companies with market caps over $50 billion.^[34] Subsequent editions used that definition until 2020,^[35] when the sixth edition redefined them as having market caps over $200 billion.^[36]

The CRSP US Mega Cap Index's inception was on April 1, 2011.^[12]

In 2011, Investing Demystified defined mega-caps as companies with market caps of at least $25 billion,^[37] whereas in the same year, The Complete Idiot's Guide to Stock Investing defined them as having market caps at least $50 billion.^[38] That's equivalent to $34 billion and $69 billion, respectively, in 2024 using GDP deflator adjustment.^[11] In 2014, Asset Allocation Demystified stated that a typical mega cap company had a market cap of over $50 billion.^[39]

The S&P 500 Top 50 Index was launched on November 30, 2015.^[40]

The Principal US Mega-Cap ETF's inception was on October 11, 2017; however, until June 10, 2022, it used a different investment strategy.^[28]

The S&P 500 Top 10 Index was launched on July 14, 2023.^[41]

The MSCI USA Mega Cap Select Index was created circa February 2024.^[10] The S&P 500 Top 20 Index was launched on August 1, 2024.^[42]

The following stocks had market caps over $200 billion in the second quarter of 2023:^[2]

• Market capitalization § Market cap terms, including large-cap and mid-cap
• Small-cap
• Microcap stock, including nano-caps
• List of public corporations by market capitalization
• Magnificent Seven (stocks)
• Market price
• Authorised capital
• Treasury stock

• Year-end market capitalization by country – World Bank, 1988–2018