Holden Karnofsky

Holden Karnofsky (born 1981) is an American grantmaker who cofounded the charity evaluator GiveWell and the foundation Open Philanthropy, the durable financial backbone of the Effective Altruism movement and of longtermist and AI-safety work. As Open Philanthropy's co-chief executive he directed the institutional patronage that sustained AI-existential-risk research, was an early backer of the AI company Anthropic, and in 2025 left grantmaking to work at Anthropic directly. He is married to Anthropic cofounder and president Daniela Amodei.¹²

GiveWell

Karnofsky and Elie Hassenfeld met as analysts at the hedge fund Bridgewater Associates, where they were part of a group of eight finance-industry friends researching charitable giving in their spare time. In 2007 the two left their jobs, raised about 300,000 dollars from former coworkers, and founded GiveWell, an organization that rates charities by the measured cost-effectiveness of their interventions and recommends a short list of top picks. The model, evidence-based giving aimed at maximizing lives saved per dollar, became one of the two intellectual streams of effective altruism, alongside the Oxford moral philosophy of Toby Ord and William MacAskill.³⁴

Months after the launch, Karnofsky was caught promoting GiveWell anonymously: in December 2007 he posted a question soliciting charity recommendations on the community site Ask MetaFilter under a false identity, then answered it touting GiveWell without disclosing his role. The board removed him as executive director and board secretary effective January 3, 2008, cut 5,000 dollars from his salary, and required him to take a professional-development course; he was later restored to the leadership. GiveWell grew into a major channel for evidence-based giving, directing more than 1.45 billion dollars to its top charities between 2009 and 2024, with roughly half of that going to the Against Malaria Foundation at an estimated cost of about 5,500 dollars per life saved.⁷⁸

Open Philanthropy

GiveWell's research into larger and riskier giving opportunities led to a partnership with Good Ventures, the foundation established in 2011 by Facebook cofounder Dustin Moskovitz and his wife Cari Tuna. The two efforts joined as the Open Philanthropy Project in 2014 and began independent operations in 2017, with Karnofsky as co-chief executive. Funded chiefly by Moskovitz and Tuna, Open Philanthropy directed more than four billion dollars in grants by 2025 across global health and "longtermism," the latter covering AI risk, pandemic preparedness, and the far future. Its AI-risk money flowed to the research community around the Machine Intelligence Research Institute, the Future of Humanity Institute, and the Rationalist Community, making Open Philanthropy the principal patron of AI-safety work outside the technology companies. The organization renamed itself Coefficient Giving in 2025.¹²

The effort began inside GiveWell as "GiveWell Labs" before splitting off, with Karnofsky and Alexander Berger sharing the chief-executive role until Berger became sole chief executive on Karnofsky's 2023 departure. In March 2017 Karnofsky steered Open Philanthropy's 30-million-dollar grant to OpenAI, a sum that bought a board seat he held until 2021, when he resigned it after his wife cofounded a competing lab. Between 2021 and 2023 Karnofsky wrote the "most important century" series on his blog Cold Takes, more than twenty essays arguing that the development of transformative AI could make the present century the most consequential in human history, a thesis that supplied the intellectual rationale for Open Philanthropy's concentration of money on AI risk.²⁹

Anthropic and the Amodei Tie

Open Philanthropy was an early funder of Anthropic, the AI company founded in 2021 by former OpenAI researchers from the effective-altruism milieu, and Karnofsky held a seat associated with that early backing. Karnofsky married Daniela Amodei in 2017; she cofounded Anthropic with her brother Dario Amodei and serves as its president. In 2022 Sam Bankman-Fried invested roughly 500 million dollars of FTX-derived capital in Anthropic through Alameda Research, placing the company at the intersection of the movement's two largest funders during the period Karnofsky's foundation and his wife's company were both tied to it. Karnofsky took a leave from his co-chief-executive role in 2023 to focus on AI strategy and joined Anthropic in January 2025 to work on its responsible-scaling and safety policies.²⁵⁶

The overlap drew the criticism that the largest funder of independent AI-safety research was led by a man married to the president of a frontier AI lab his foundation had financed. Karnofsky's OpenAI board seat from 2017 to 2021 had already placed him inside one leading lab before the marriage tie connected him to a second; commentators noted that the same small network of effective-altruism figures sat on the funding, governance, and research sides of the field at once. At Anthropic he took up work on the company's Responsible Scaling Policy, the framework of capability thresholds and safety commitments the company uses to govern the release of more powerful models.²⁶