StackOne raises $20M for easier API integration, led by Big Tech backers

London-based StackOne has raised $20M in a Series A round led by GV (formerly Google Ventures), with participation from Workday Ventures, XTX Ventures, Episode 1, Playfair, and angel investors from OpenAI, DeepMind, Microsoft, and Mulesoft.

The round brings StackOne’s total funding to $24M. The company enables business to integrate multiple APIs into their own platform.

In an increasingly interconnected B2B software landscape, the ability to integrate quickly and securely with a vast range of APIs has become a make-or-break factor for product teams. StackOne is targeting this problem with a proprietary AI agent that enables faster, more scalable integration workflows.

“For over a decade, Guillaume and I have felt the acute pain of integrations. We’d see teams burn months rebuilding or refusing requests and nothing on the market eased this pain. So we, alongside a super talented and passionate team, built it ourselves,” said Romain Sestier, co-founder and CEO of StackOne.

“StackOne doesn’t just reinvent how integration platforms can and should be built – with depth, accuracy and security by default – but we believe AI agents are the missing piece in finally delivering enterprise-grade integrations at scale.”

“Integrations are now table stakes for winning and keeping customers in B2B SaaS, especially for the ever-growing swathe of AI agents,” added Guillaume Lebedel, co-founder and CTO. “StackOne solves all of this in a single layer; one that marks the birth of a new generation of integrations platform for an AI-first world.”

According to market analysts, the enterprise application integration market is projected to reach $17.5B by 2033, driven by the proliferation of SaaS tools, the rise of AI agents, and mounting demand for seamless data flow across business units.

With the new capital, StackOne plans to scale its platform’s AI capabilities, expand integration coverage, and support a growing community of AI developers. The company is also investing in open-source projects and hosting events like AI Demo Days to accelerate knowledge-sharing across the AI integration ecosystem.