John O'Sullivan
General Partner @ Act Venture Capital
John O'Sullivan is a Series A investor at Act Venture Capital focused on Software and Payments. John is a Director of ACT Venture Capital and has been active in operating roles and venture investing for 20 years.John is currently on the boards of Adeptra, S3 Group, Frontier Silicon & Novate Medical and works with the teams at Swrve, Digit Gaming, Biosensia, Worldnet, Storyful and Cloudium.Previously, he was on the board of Kymata(acquired by Alcatel), AGI Therapeutics plc (acquired by Vidara Therapeutics), Firecomms (acquired by ZJF Group) and Intense Photonics and was involved with a number of other ACT investments.Prior to joining ACT, John worked with a range of start-up companies through the state indigenous development agency, Enterprise Ireland. Prior to that he held a number of business and operating roles with Misys plc, Kindle Banking Systems and KAO Info-systems.He graduated from University College Cork (UCC) with a degree in Commerce and also holds an ACCA Certified Diploma in Financial Management.John is an Adjunct Fellow at the UCC Business School.
- Total investments:
- 15
- Last investment:
- Lead investor:
- 47%
Last updated:
For AI agents: llms.txt
Industries John O'Sullivan invests in
Stages John O'Sullivan invests in
Countries John O'Sullivan invests in
Contacts
| Type | Contact | Validation |
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| Personal email | ||
| Work phone | ||
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| Socials |
Investment Focus
Industry
- Software 5 (33%)
- Payments 2 (13%)
- E-Commerce 2 (13%)
- Health Care 2 (13%)
- Digital Media 2 (13%)
Stage
- Series A 5 (33%)
- Venture - Series Unknown 3 (20%)
- Seed 2 (13%)
- Funding Round 2 (13%)
- Series B 1 (7%)
Country
- Ireland 6 (40%)
- United States 2 (13%)
- United Kingdom 1 (7%)
Investments
| Company | Description | Round | Links |
|---|---|---|---|
| Founded in 2017, Deciphex aims to transform diagnostic workflows through AI-powered digital pathology to improve patient outcomes worldwide. Its two flagship platforms target distinct markets: Diagnexia connects global subspecialty pathologists for rapid diagnostics and backlog reduction, while Patholytix accelerates drug development throughoptimized preclinical safety assessments. By automating routine tasks, these platforms enable pathologists to focus on complex cases while delivering faster, more reliable diagnoses. Through this combination of AI innovation and clinical expertise, Deciphex is advancing both healthcare delivery and therapeutic development. | $32.1M / Series C / Jan 07, 2025 | ||
| Good Travel Software has developed innovative booking software for the car share industry. Car sharing is a young high growth industry that exists in 600 cities worldwide and it allows customers to rent cars by the minute. Our software, Drop Car, introduces scheduled one-way bookings and dynamic pricing to the industry. Drop Car is sold as a pluginto existing car share booking software and is targeted at large car share companies. Drop Car was completed in early 2012, having been tested in Europe, and we have recently signed up our first customer, a German car share company. | Venture - Series Unknown / Apr 04, 2023 | ||
| Founded in 2017, Deciphex aims to transform diagnostic workflows through AI-powered digital pathology to improve patient outcomes worldwide. Its two flagship platforms target distinct markets: Diagnexia connects global subspecialty pathologists for rapid diagnostics and backlog reduction, while Patholytix accelerates drug development throughoptimized preclinical safety assessments. By automating routine tasks, these platforms enable pathologists to focus on complex cases while delivering faster, more reliable diagnoses. Through this combination of AI innovation and clinical expertise, Deciphex is advancing both healthcare delivery and therapeutic development. | $11.5M / Series B / May 19, 2022 | ||
| PlasmaBound provides a step-change technology, termed Controlled Plasma Ablation (CPA), which facilitates the structural adhesive joining of lightweight materials, namely carbon and glass fibre reinforced composites. CPA technology will accelerate the use of these lightweight composite materials into multi-material structural assemblies, byenabling reliable adhesive joining which is stronger than the composite structures themselves. | $2.5M / Venture - Series Unknown / May 01, 2022 | ||
| Founded in 2017, Deciphex aims to transform diagnostic workflows through AI-powered digital pathology to improve patient outcomes worldwide. Its two flagship platforms target distinct markets: Diagnexia connects global subspecialty pathologists for rapid diagnostics and backlog reduction, while Patholytix accelerates drug development throughoptimized preclinical safety assessments. By automating routine tasks, these platforms enable pathologists to focus on complex cases while delivering faster, more reliable diagnoses. Through this combination of AI innovation and clinical expertise, Deciphex is advancing both healthcare delivery and therapeutic development. | $6.2M / Series A / Jul 16, 2020 | ||
| Effective Software are the companybehind health+safety (part of theManagement Plus range includinglearn assess) and provide leadingweb-based safety software solutionsand training and assessmentplatforms. Moving away fromtraditional outdated systems weprovide truly affordable andcomprehensive cloud-based solutionsfor small andmedium businesses.Our range of products available coverRisk Management, DSE Assessments,Plant & Asset Management, Audits &Inspections, Training Management &E-Learning and much more. | $1.5M / Series A / Dec 29, 2019 | ||
| Founded in 2017, Deciphex aims to transform diagnostic workflows through AI-powered digital pathology to improve patient outcomes worldwide. Its two flagship platforms target distinct markets: Diagnexia connects global subspecialty pathologists for rapid diagnostics and backlog reduction, while Patholytix accelerates drug development throughoptimized preclinical safety assessments. By automating routine tasks, these platforms enable pathologists to focus on complex cases while delivering faster, more reliable diagnoses. Through this combination of AI innovation and clinical expertise, Deciphex is advancing both healthcare delivery and therapeutic development. | $2.6M / Venture - Series Unknown / Apr 15, 2019 | ||
| Worldnet TPS is a Multi-Channel Online Payment gateway, providing payment services to domestic and international eCommerce, mCommerce and Social commerce merchants. Worldnet TPS is based in Dublin, along with the European Headquarters of the many Web 2.0 companies, including Google and Facebook Founded in 2007, WorldNet TPS has developed asoftware-based host solution, to provide a single source of sophisticated, robust and highly scaleable payment and transaction processing services. This solution, based on the latest IP technology, has both multi-lingual and multi-currency processing capabilities.Worldnet has since achieved significant product and service differentiation with the delivery of On-line Dynamic Currency Conversion (eDCC), Recurring Payment, Fraud Management and alternative payment methods, through a range of alliance agreements with International payment processing platforms and specialist service providers.Worldnet TPS has established itself in the international online payments industry through adopting the motto “Differentiation through innovationâ€. | Series A / Aug 10, 2017 | ||
| Worldnet Payments is a software provider that designs and develops frictionless payment solutions for seamless omnichannel payments. | Series A / Aug 10, 2017 | ||
| SilverCloud Health provides immediate access to evidence-based and supported digital therapies. SilverCloud’s engagement has shown a three-fold increase in client/patient engagement and a three-fold decrease in client/patient program dropout when compared with current leading online therapeutic products. It was founded in 2011 andheadquartered in Boston, Massachusetts. | $8.1M / Series A / Jan 18, 2017 | ||
| See all 15 investments → | |||
Co-Investors
About Act Venture Capital
Technology-focused, investing capital and expertise to fuel growth in the most promising ideas and companies. Raised c.€600m across multiple funds and invest from seed to growth. We look for companies with potentially cutting-edge, category-defining businesses in markets including application software, IT infrastructure, communications, Internet and mobile. We help founders create and scale businesses globally. We work as a small team with diverse strengths accessing a community of over 200 founders. The teams and companies we back scale their investor base as they scale their business execution and ambition. We work closely with them in this process. Over the past 25 years have built a broad network of US and European investors and founders that share our vision and approach. Act is based in Dublin, Ireland. Our most recent funds are supported by the European Investment Fund.
Act Venture Capital Contacts
| Name | Phone | Socials | |
|---|---|---|---|
Andrew O Neill
Principal
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Conor Mills
Principal
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Debbie Rennick
General Partner
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John O'Sullivan
General Partner
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Sarah Matthews
Financial Control
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FAQ
What does John O'Sullivan invest in?
John O'Sullivan invests primarily in Software, Payments and E-Commerce startups, most often at Series A and Venture - Series Unknown stage. Most of the 15 investments tracked by Shizune back companies in Ireland. The Investment Focus section breaks down every industry, stage and country in the portfolio.
How do I contact John O'Sullivan?
Public channels for John O'Sullivan include LinkedIn. For a verified work email and phone number, create a free Shizune account — contact data is searched across 20+ sources and validated before delivery, so your outreach lands in the right inbox.
When did John O'Sullivan last invest?
The most recent investment recorded for John O'Sullivan closed in Jan 2025. Shizune tracks 15 investments in total for this profile, including round sizes, stages and portfolio companies, all sourced from confirmed public funding rounds and refreshed monthly.
Is Shizune's investor data accurate?
Yes — every stat on this profile is calculated from confirmed public funding rounds monitored across hundreds of sources since 2020. This profile was last refreshed in Oct 2026 and is updated monthly. Spotted something off? Use the “Suggest an edit” link near the top of the page.
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