We took a break from covering the largest U.S. startup investments over Thanksgiving week, which was just as well, given that it was a predictably slow period for big deal announcements. Now, with just a few weeks left in 2025, things are picking up again. Predictions market Kalshi led the list after confirming its already widely reported $1 billion fresh financing. Other big rounds came from sectors including defense tech, AI infrastructure, cybersecurity and biotech. 1. Kalshi, $1B, predictions market: A couple weeks ago, we included Kalshi in our Top 10 after the company reportedly secured $1 billion in fresh funding. Well, now it's official, with confirmation from the fast-growing New York-based predictions marketplace. Crypto-focused investor Paradigm led the financing, with participation from a long list of venture firms. 2. Castelion, $350M, defense tech: Castelion, a developer of hypersonic munitions, says it raised $350 million in Series B financing led by Altimeter Capital...
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