The Biggest IPO in Stock Market History Is Here. What It Means for Your Portfolio.

The SpaceX (NASDAQ: SPCX) initial public offering (IPO) is finally here, and whether you invest in it directly or not, this historic event is likely to impact your portfolio. I say it's historic because it is expected to raise $75 billion for the company, the largest-ever initial public offering.

Whether you've sworn off the IPO, were the lucky recipient of IPO shares, or are planning to buy some as soon as you can, here's what you need to know about the bigger picture.

The markets could be volatile

It's not just the size of the offering that's huge; the company's total value is expected to start at $1.8 trillion, and it could soar much higher on the first day of trading. A new stock of that size can't go by unnoticed.

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Prediction sites are already calling the IPO for over $2 trillion. Pre-IPO futures on crypto exchange Hyperliquid are predicting $2.1 trillion right now, although traders on Polymarket only give it a 5% chance of breaking through $3 trillion.

The S&P 500 has been down this week, and although the decline began with a positive jobs report last Friday, investors might be preparing their funds to buy SpaceX stock. Depending on what happens over the next few days, there could be ripples throughout the market.

It's going to be included in several indexes

If you own exchange-traded funds (ETFs) that track the Nasdaq-100 or the Russell 1000, you might be buying SpaceX stock faster than you think. The Nasdaq and FTSE Russell changed their rules to include it sooner than existing regulations allowed, and it might be added to the Russell 1000 as early as five days from now. New rules might also expand its presence in the Nasdaq-100.

ETFs like the popular Invesco QQQ Trust, which tracks the Nasdaq-100, will have to reallocate their funds to reflect changes in the index.

Not only will these moves add SpaceX to the ETFs, but they could also impact SpaceX's price, as they have to buy so much stock to reflect the changes.

The Invesco ETF, for example, has $460 billion in assets under management. It's the second-most traded ETF on the market, which could add further volatility to the stock and to the market as a whole. It's a weighted index, with its top positions in Nvidia (8.7%), Apple (7.7%), and Microsoft (5.7%), and those stakes will look very different once SpaceX gets in.

Vanguard has three separate ETFs that track the Russell 1000: the Russell 1000 ETF, the Russell 100 Growth ETF, and the Russell 1000 Value ETF, and many other companies have similar index funds. All these ETFs will be buying SpaceX once it's included in the index.

It's not going to be included in the S&P 500 -- yet

S&P Global, the company that owns the S&P 500, has declined to change its regulations to include SpaceX stock. To be included, stocks need to be on the market for at least one year and be profitable, in addition to other requirements.

That will provide some measure of stability for at least a year, when SpaceX stock might be eligible to join the broader index if it's profitable. It reported a $4.9 billion loss in 2025 and a $4.3 billion loss in the 2026 first quarter.

It's just another moment in stock market history

These are short-term factors, although they could be significant over the next few days or weeks. If you're a long-term investor who's well-diversified among classes and categories, this IPO ultimately won't make a difference in your portfolio. If the SpaceX IPO does end up inducing heavy market volatility, the important thing is to remain calm and not panic sell.

Jennifer Saibil has positions in Apple. The Motley Fool has positions in and recommends Apple, Hyperliquid, Microsoft, Nvidia, and S&P Global. The Motley Fool has a disclosure policy.