These 3 Stocks Led the S&P 500 in September 2025

The S&P 500 experienced its strongest September in 15 years, gaining 3.5%, primarily driven by strong performances in technology stocks. Warner Bros. Discovery (WBD) surged 67.8% on takeover speculation, while AppLovin (APP) rose 50.1% following its S&P 500 inclusion and analyst upgrades, though it now faces an SEC probe regarding data collection practices. Western Digital (WDC) also climbed 49.4%, benefiting from booming demand for data storage fueled by artificial intelligence and cloud computing, alongside multiple analyst price target increases.

Analysis

The S&P 500 recorded its strongest September in 15 years, gaining 3.5%, with technology stocks leading the advance. Warner Bros. Discovery (WBD) surged 67.8% during the month, driven by takeover speculation following a Wall Street Journal report of a potential "majority cash bid" from Paramount Skydance. WBD also plans to split into two companies by mid-2026, separating its streaming and studio businesses from global TV networks.

AppLovin (APP) saw a 50.1% increase in September, primarily due to its inclusion in the S&P 500 index and subsequent analyst price target upgrades. However, the stock is now facing pressure after a Bloomberg report indicated an SEC probe into its data collection practices, introducing regulatory uncertainty.

Western Digital (WDC) shares climbed 49.4% in September, reaching a 52-week high of $137.40. This performance was fueled by booming demand for data storage, driven by artificial intelligence and cloud computing, with at least seven analysts raising price targets. Morgan Stanley notably increased its price target from $99 to $171, citing the stock's low valuation relative to the significant potential demand for HDDs amid rising cloud spending.

Key Decisions for Investors

• Investors in Warner Bros. Discovery should closely monitor developments regarding the potential takeover bid and the planned corporate split, as these are significant catalysts for future valuation.
• For AppLovin, it is prudent to track the progress and potential implications of the SEC probe into data collection practices, as regulatory outcomes could introduce material risk.
• Consider Western Digital for exposure to secular growth in AI and cloud-driven data storage demand, given its strong market position and positive analyst sentiment.