20 US AI Startups That Raised $100M or More in 2025

If you've been paying attention to venture capital news, you know 2025 has been extraordinary. But what makes this year genuinely historic isn't just the volume of mega-rounds. It's the velocity. The 20 most successful US AI startups have raised $100 million or more in 2025, and most of them returned for second, third, or even fourth mega-rounds within the same calendar year.

This signals something fundamental has shifted in how capital flows to AI companies. When startups close billion-dollar rounds and return for more capital within months, it suggests investors believe AI's path to massive market disruption is imminent.

These 20 companies span foundation models, healthcare, legal tech, infrastructure, and specialized AI agents. What unites them isn't sector, but demonstrated velocity. They're raising capital faster, deploying it immediately into compute and talent, and scaling customer adoption simultaneously. This isn't normal venture capital behavior. This is a different paradigm entirely.

The Mega-Round Elite: Meet the 20 Companies

Here are the 20 US AI startups that raised $100M or more in 2025, ranked by capital raised:

1. Anthropic - $13 billion Series F (September 2025); Focus: Foundation model and AI research company
2. Anysphere (Cursor) - $2.3 billion Series C (November 2025); Focus: AI-powered code editor for developers
3. Reflection AI - $2 billion Series B (October 2025) Focus: Reasoning and inference optimization
4. Cerebras Systems - $1.1 billion Series G (September 2025); Focus: AI chip technology and hardware
5. Harvey - $300 million Series E (June 2025, second round); Focus: Legal AI and professional services automation
6. Abridge - $300 million Series E (May 2025, second round); Focus: Healthcare ambient documentation and AI
7. Periodic Labs - $300 million Seed (September 2025); Focus: AI scientist and research automation
8. Lila Sciences - $350 million Series A (October 2025); Focus: Science superintelligence platform
9. OpenEvidence - $200 million Series C (October 2025, second round); Focus: Medical AI chatbot and healthcare applications
10. Runway - $308 million Series D (May 2025); Focus: Generative media and video creation
11. Together AI - $305 million Series B (July 2025); Focus: Open-source AI infrastructure and models
12. EliseAI - $250 million Series E (August 2025); Focus: Healthcare and housing automation
13. Fireworks AI - $250 million Series C (October 2025); Focus: Open-source model deployment platform
14. Suno - $250 million Series C (November 2025); Focus: AI music generation
15. Modular - $250 million Series B (September 2025); Focus: AI compiler and systems software
16. Harmonic - $100 million Series B (July 2025); Focus: Mathematical reasoning engine
17. Parallel - $100 million Series A (November 2025); Focus: Web infrastructure for AI agents
18. Tennr - $101 million Series C (March 2025); Focus: Healthcare AI and clinical decision support
19. Ambience Healthcare - $243 million Series C (June 2025); Focus: Ambient clinical documentation
20. Lambda - $480 million Series D (2025); Focus: Cloud infrastructure for AI training and deployment

Why These 20? The Pattern Behind the Capital

The distribution across these 20 companies reveals what investors truly believe will generate returns. Healthcare AI claims the largest sector concentration, with Abridge, OpenEvidence, Ambience Healthcare, EliseAI, and Tennr collectively accounting for over $1.3 billion in capital.

These companies share a common advantage: they solve genuine market problems with measurable ROI. Healthcare systems track outcomes. When AI reduces administrative overhead or catches diseases earlier, the financial impact is quantifiable.

Foundation models and reasoning engines command the highest valuations. Anthropic's $183 billion valuation and Anysphere's $29.3 billion valuation reflect investor conviction that these platforms will serve as infrastructure layers supporting entire ecosystems.

Reflection AI's $8 billion valuation for a Series B represents extraordinary confidence in reasoning-focused models emerging as the next frontier of capability.

Infrastructure companies received aggressive capital deployment. Cerebras, Lambda, Together AI, and Modular collectively raised over $2 billion. This concentration reflects a fundamental reality: building frontier AI requires staggering computational resources.

GPUs are supply-constrained. Every quarter brings more advanced chips. Investors want portfolio companies to access newest hardware immediately. Waiting six months means competitors gain training advantages. This creates pressure to raise constantly.

The Velocity Factor: Why 2025 Is Different

What distinguishes 2025 from previous venture cycles is capital velocity. Multiple companies in this elite group raised mega-rounds twice within the same year. Harvey and Abridge each secured two $300 million rounds in 2025. Anthropic raised $3.5 billion in March then returned for $13 billion in September. OpenEvidence closed rounds in March and October.

This pattern is unprecedented. Historically, venture capital operates on annual funding cycles. Startups raise Series A, operate for 18-24 months, then raise Series B. The 2025 AI landscape operates on quarterly cycles. Companies raise capital, deploy it into compute immediately, hit growth milestones within months, then return for additional capital.

Why? The answer reveals AI's unique capital dynamics. Training large models requires constant access to the newest chips. Cloud providers release incremental hardware improvements quarterly.

Startups that secure capital quickly can purchase hardware ahead of competitors, gaining training advantages. Those advantages compound quickly into customer acquisition, revenue growth, and market dominance. Delaying capital raises means falling behind. This creates rational incentive to raise constantly and deploy aggressively.

The Infrastructure Play: Why Strategic Investors Matter

What's often overlooked is the role of strategic investors in these mega-rounds. Nvidia, Google, Amazon, and Microsoft appear across dozens of these companies' cap tables. These aren't pure venture capital investments. They're ecosystem plays combining equity with multi-year cloud credits, model distribution agreements, and compute commitments.

When Nvidia co-leads a mega-round and provides GPU credits, the startup gains access to hardware at favorable terms and gains credible signals to enterprise customers. When Google invests and signs a cloud partnership, the startup gets immediate infrastructure support.

These packages accelerate growth beyond what venture capital alone can deliver. Startups attracting strategic investment grow faster, achieve traction quicker, and become acquisition targets or strong late-stage investments.

This creates compounding advantage. The 20 companies in this elite group nearly all secured strategic investment. The startups that didn't struggle competing against those that did.

Capital Concentration: The Real Story

Here's what matters most: capital is concentrating at unprecedented levels. These 20 companies will capture the vast majority of AI's near-term value creation. Thousands of other AI startups will compete for shrinking downstream funding.

Most will never raise $100 million. Most will become acquihires or remain in zombie state, operating with minimal capital while competing against mega-funded companies.

With GPU prices sustained and competition intensifying, investors are now digging into unit economics. Can companies actually monetize these products? Are margins sustainable? Do they have defensible advantages? The answers determine whether 2025's mega-round activity continues or crashes. Most AI applications currently operate on thin margins because cloud providers subsidize inference. If those subsidies end, many startups will face profitability crises.

The 20 companies in this list will likely survive this transition. They have diversified revenue sources, proprietary data advantages, or irreplaceable integrations into customer workflows. The question is whether they can deploy mega-round capital effectively to build sustainable competitive moats.

Fast Facts: The 20 US AI Startups Raising $100M+ Explained

What defines the elite 20 US AI startups that raised $100M+ in 2025?

The elite 20 US AI startups represent the highest capital concentration in venture history, spanning foundation models, healthcare, legal tech, and infrastructure. Most secured multiple mega-rounds within the same year, signaling unprecedented capital velocity in AI investment cycles.

Why do mega-round US AI startups raise multiple times annually in 2025?

US AI startups raised multiple mega-rounds because GPU supply constraints create quarterly competitive advantages. Startups deploying capital immediately access newest chips faster than competitors, compounding training and deployment advantages into customer acquisition and market dominance.

What limits the 20 mega-funded US AI startups from achieving profitability quickly?

Despite massive funding, these US AI startups face margin compression from cloud provider discounts, intense competition reducing pricing power, and uncertain long-term monetization as adoption accelerates. Without sustainable unit economics or defensible advantages, profitability remains elusive despite mega-round capital.