SOSV
About SOSV
SOSV was founded by Sean O'Sullivan. Public sources found do not give a founding year. The firm reported about $1.5 billion in assets under management and more than 1,000 portfolio companies as of January 2024. Its programs operate from New York City, Newark and San Francisco, with additional offices in Cork, Pune, Shenzhen and Tokyo. SOSV raised $277 million for its SOSV IV fund in December 2019, up from $150 million for SOSV III. In April 2024 it closed SOSV V at $306 million, its largest fund to date. Crunchbase lists SOSV as an active, private firm with 101 to 250 employees. PitchBook counts 40 professionals and 2,795 investments to date.
SOSV's portfolio page groups some companies under a Physical AI theme. These are firms that combine AI with robotics, hardware and advanced manufacturing so that machines can sense, decide and act in the physical world. PitchBook names NatLean, Danu Robotics and Zenithon AI among SOSV's investments. Lounge's deals desk records a $10M seed round for Zenithon in September 2026.
SOSV says it invests from the earliest stage and also joins seed, Series A and later rounds, with ongoing support for founders. Its HAX and IndieBio programs are pre-seed. Slidebean, a third-party listing, gives a pre-seed and seed range of $250K to $525K. VCBacked, another third-party tracker, puts the average HAX investment at $1.5M across 95 companies. No check sizes appeared on the firm's own pages I found.
- Zenithon AI: seed round of $10M, September 2026 (Lounge deals desk)
- Danu Robotics: listed among SOSV investments on PitchBook; round and date not confirmed
- NatLean: listed among SOSV investments on PitchBook; round and date not confirmed
Investing activity
SOSV appears in 1 AI deal tracked by the AI Lounge deals desk, rounds totalling $10M. The rounds are mostly Seed, with a median round size of $10M. The most recent is Zenithon (Seed, $10M, Sep 2026).
SOSV most often invests alongside Seraphim, MMC Ventures and Lunar Ventures, and the companies it backs on AI Lounge are mostly in AI.
Deals
Frequently asked questions about SOSV
Does SOSV invest in AI startups?
Yes. SOSV's portfolio page has a Physical AI theme covering companies that pair AI with robotics and hardware. Zenithon AI, which raised a $10M seed round in September 2026, is one example.
What funds has SOSV raised?
SOSV IV raised $277 million in December 2019. SOSV V closed at $306 million in April 2024 and is the firm's largest fund to date.
What stages does SOSV invest in?
SOSV runs pre-seed programs through HAX and IndieBio and says it also joins seed, Series A and later rounds. Founders should confirm current terms with the firm.
How much does SOSV invest per startup?
SOSV has not published check sizes on its own site. Third-party trackers cite a $250K to $525K pre-seed and seed range and a $1.5M average for HAX investments.
Where is SOSV based?
SOSV is listed with its headquarters in Princeton, New Jersey. Its programs run from New York City, Newark and San Francisco.
What AI companies has SOSV invested in?
SOSV's AI investments include Zenithon. The 1 round on AI Lounge are listed on this page with amounts, dates and co-investors.
What stage does SOSV invest at?
In the rounds tracked on AI Lounge, SOSV has invested at Seed, with a median round of $10M.
Who does SOSV co-invest with?
SOSV's most frequent co-investors on AI Lounge are Seraphim (1 deal), MMC Ventures (1 deal) and Lunar Ventures (1 deal).
How can founders reach SOSV?
Founders on AI Lounge can see SOSV's contact details in AI Investor Contacts (paid plans), check for a warm introduction through members who worked with the firm under Warm Paths, and add SOSV to their Investor Pipeline to track the conversation.