These Were the 3 Top-Performing Stocks in the S&P 500 in September 2025 -- and One Popped 68%!

Key Points

• These three stocks were standout performers in September.

• Each has more room to grow.

• But don't expect double-digit growth each month.

• 10 stocks we like better than Warner Bros. Discovery ›

The S&P 500 index of 500 of America's biggest companies gained a solid 3.5% in September -- its fifth consecutive monthly gain. If 3.5% doesn't seem like a lot, remember that it's just a month's gain. (For comparison, it gained 1.9% in August.) If it were to rise 3.5% every month, that would compound to an incredible 51% annual gain.

The top-performing stocks of the month were Warner Brothers Discovery (NASDAQ: WBD), AppLovin (NASDAQ: APP), and Western Digital (NASDAQ: WDC). Here's a look at each.

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Image source: Getty Images.

Warner Brothers Discovery surged 68.1% in September. With brands under its roof including HBO, HGTV, Discovery, CNN, TNT, and the Food Network, it's the result of a 2022 joining of WarnerMedia and Discovery Communications. More recently, it has announced plans to split in two. On top of that, there's a rumor of a buyout.

AppLovin, up 49.2% in September, recently carried a market value of $243 billion. It offers software that helps app developers profit more from their apps -- largely via advertising -- and it's succeeding internationally, too. The 49% jump is impressive, but not as eye-opening as its three-year average annual gain of 233%. Bulls are excited that it's moving beyond the realm of gaming apps. It was recently added to the S&P 500, as well.

Western Digital, which popped 46.6% in September, is a hard disk drive specialist, and data storage is a hot market lately, boosted by increasing demands from the growth of both cloud computing and artificial intelligence (AI). Several investment banks increased their price targets for the company in September.

Check any of these companies out if your interest is now piqued.

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Selena Maranjian has positions in Warner Bros. Discovery. The Motley Fool has positions in and recommends Warner Bros. Discovery. The Motley Fool has a disclosure policy.