After a record-shattering 2024, the U.S. artificial intelligence sector is proving that investor appetite for mega-rounds isn’t slowing in 2025.
In 2024, 49 AI startups closed rounds worth $100 million or more, with seven raising $1 billion or higher. This year is already rivaling that pace: by late Q3, multiple billion-dollar raises have been confirmed, alongside dozens of nine-figure deals across healthcare, infrastructure, and research labs.
The biggest single round so far belongs to OpenAI, which closed a historic $40 billion raise in March, valuing the company at $300 billion. Anthropic followed with a $3.5 billion round at a $61.5 billion valuation, while Thinking Machines Lab surprised the industry with a $2 billion seed round, backed by Andreessen Horowitz, Nvidia, and AMD.
Healthcare continues to dominate funding: Abridge raised two rounds this year ($250M and $300M), Ambience Healthcare pulled in $243M, OpenEvidence secured $210M, and EliseAI landed $250M. AI-driven drug discovery player Insilico Medicine added another $110M to its war chest.
Infrastructure is another hot spot: Lambda raised $480M, Celestial AI secured $250M, and TensorWave closed $100M for its AI compute stack. Enterprise tools also drew big checks, with Glean raising $150M at a $7.25B valuation and Harvey securing two separate $300M rounds this year.
Media and creative AI remain investor darlings: Runway ($308M), Fal ($125M), and ElevenLabs ($180M) all added significant runway in 2025. Meanwhile, experimental players like Reflection.Ai ($130M) and Lila Sciences ($200M) are betting on superintelligence platforms.
Even benchmarking and community-driven tools are attracting mega-rounds. LMArena scored a $100M seed round at a $600M valuation, signaling how broad the AI investment thesis has become.
Related: Europe Sees 12 New Unicorns in 2025 as Funding Season Resumes
With the fourth quarter still ahead, 2025 is on track to surpass last year’s totals, not just in dollars raised, but in the breadth of AI sectors drawing heavy venture capital. From legal AI to healthcare LLMs to frontier model labs, the U.S. AI boom shows little sign of cooling.
