Michael Callahan
About Michael Callahan
Michael Callahan is based in Palo Alto, California. Crunchbase lists him as an Entrepreneur in Residence at Greylock Partners. He was CTO of PolyServe, a Greylock portfolio company that built shared-data storage clustering software for Linux and Windows. HP acquired PolyServe in 2007.
Before PolyServe he was Director of Advanced Development at Ask Jeeves. PitchBook's profile says he graduated summa cum laude from Harvard, and that he was a Rhodes Scholar and a Junior Research Fellow in Mathematics at Oxford.
Tracxn lists him as a co-founder of Awake Networks, which it dates to 2014. A 2024 SiliconANGLE article describes him as a board member of Datadog.
Crunchbase shows 7 personal investments across 6 portfolio companies. PitchBook lists 9 investments and 3 exits for an individual angel by the same name, using a profile that matches his background. The two databases count differently, so treat the numbers as approximate.
He often appears in angel lists alongside operators and security founders. In Prime Security's 2024 seed round he was named with other angels, and in Tolmo's 2026 round he was listed with executives from Datadog, Tenable and Cloudflare.
On the Lounge deals desk, Callahan took part in the $22M Tolmo seed and the $6M Clario seed, both in June 2026.
Tolmo is a San Francisco AI security company in Y Combinator's Spring 2026 batch. Accel led the round, with Y Combinator participating. Clario is an enterprise data platform that finds redundant, obsolete and trivial files, which it says hurt AI performance. Preface Ventures led its round.
Crunchbase also lists Patronus AI, where he appears in both a seed and a Series A round, though the dates are not public. Prime Security's $6M seed, announced in October 2024, describes an AI-powered design-stage security platform.
His public record is early stage: seed rounds, plus one Series A at Patronus AI and one at Lupa Pets. The companies skew toward enterprise software, security, data infrastructure and AI tooling. Tracxn lists his top sectors as Enterprise Applications and Enterprise Infrastructure, and his investment locations as the United States, the United Kingdom and one more. His companies include startups with teams in San Francisco, New York and Tel Aviv.
I found no public statements from him about his check size or what he looks for in a pitch.
- Tolmo: AI security platform with agents across code, CI and cloud; $22M seed led by Accel, June 2026.
- Clario: platform that removes redundant, obsolete and trivial enterprise data; $6M seed led by Preface Ventures, June 2026.
- Patronus AI: AI company listed on Crunchbase with a seed and a Series A; dates not public.
- Prime Security: design-stage security platform; $6M seed led by Foundation Capital, October 2024.
- Dgraph Labs: listed on Crunchbase with a seed round; date not public.
- Lupa Pets: listed on Crunchbase with a Series A; date not public.
- crunchbase.com/person/michael-callahan-2
- pitchbook.com/profiles/investor/120687-04
- tracxn.com/d/people/michael-callahan/__MLZRfGZMdTa4yRwifC463BLoFsQJVsx
- siliconangle.com/2024/10/09/prime-security-launches-ai-powered-design-
- dealroom.co/companies/tolmo
- tooljunction.io/ai-tools/tolmo
- pulse2.com/clario-raises-6-million-seed-round-to-eliminate-enterprise-
- citybiz.co/article/861883/clario-launches-with-6m-seed-round-to-clean-
Investing activity
Michael Callahan appears in 2 AI deals tracked by the Lounge deals desk, rounds totalling $22M. The rounds are mostly Seed, with a median round size of $22M. The most recent are Tolmo (Seed, $22M, Jun 2026) and Clario (Seed, $6M, Jun 2026).
Michael Callahan most often invests alongside Accel, Y Combinator, Motier Ventures and Mark Anderson, and the companies they back on Lounge are mostly in AI.
Deals
Frequently asked questions about Michael Callahan
Does Michael Callahan invest in AI startups?
Yes. He took part in the $22M Tolmo seed, an AI security company, and the $6M Clario seed, an enterprise data company, both in June 2026. Crunchbase also lists Patronus AI in his portfolio.
What stage does Michael Callahan invest in?
His public record is mostly seed, including Tolmo, Clario, Prime Security and Dgraph Labs. Crunchbase also lists Series A rounds at Patronus AI and Lupa Pets.
What is Michael Callahan's check size?
His check size is not public. The sources I found only give the total round sizes, such as $22M for Tolmo and $6M for Clario.
Who is Michael Callahan the angel investor?
He is a Palo Alto-based investor who was CTO of PolyServe, a Greylock portfolio company acquired by HP in 2007. He has also been an Entrepreneur in Residence at Greylock and worked at Ask Jeeves.
What sectors does Michael Callahan back?
His known investments are in security, enterprise data and infrastructure, and AI evaluation. Examples are Tolmo, Prime Security, Clario and Patronus AI.
Is Michael Callahan an angel investor?
Yes. Michael Callahan invests personally as an angel.
What AI companies has Michael Callahan invested in?
Michael Callahan's AI investments include Tolmo and Clario. The 2 rounds on Lounge are listed on this page with amounts, dates and co-investors.
What stage does Michael Callahan invest at?
In the rounds tracked on Lounge, Michael Callahan has invested at Seed, with a median round of $22M.
Who does Michael Callahan co-invest with?
Michael Callahan's most frequent co-investors on Lounge are Accel (1 deal), Y Combinator (1 deal), Motier Ventures (1 deal), Mark Anderson (1 deal) and Jason Lemkin (1 deal).
How can founders reach Michael Callahan?
Founders on Lounge can see Michael Callahan's contact details in AI Investor Contacts (paid plans), check for a warm introduction through members who worked with them under Warm Paths, and add Michael Callahan to their Investor Pipeline to track the conversation.