Michael Seibel (born October 7, 1982) is a partner at Y Combinator, a prominent startup accelerator, and the co-founder of two notable technology companies: Justin.tv/Twitch and Socialcam. He first joined Y Combinator in 2013 and served as CEO of its startup accelerator from 2016 to 2024, during which he advised hundreds of startups, including many in the artificial intelligence space. Seibel is widely recognized as one of the most influential Black investors and startup mentors in Silicon Valley, noted for his advocacy of underrepresented founders and leadership in expanding access to the startup ecosystem.
Seibel's career spans entrepreneurship, investing, and board service. He has been a key figure in the growth of Y Combinator, helping to launch global programs and online initiatives that opened mentorship and resources to founders worldwide. His personal investments include several high-profile startups, and he has held board seats at Reddit and Dropbox.
Education and startups
Seibel was born in Brooklyn and moved to East Brunswick, New Jersey as a pre-teen, graduating from East Brunswick High School in 2000. At Yale University, he majored in political science and became friends with Justin Kan. He was active in Yale's Black Student Alliance and has spoken about being one of few Black students pursuing tech entrepreneurship at the university. After graduating in 2005, he worked as the finance director for Kweisi Mfume's unsuccessful run for the U.S. Senate in 2006.
He then moved to Silicon Valley to co-found Justin.tv, a live video streaming platform, and became its CEO from 2007 to 2011. He subsequently became CEO of Socialcam, a social video-sharing app launched in March 2011 that was widely referred to as "Instagram for video" in the tech press. Socialcam sold to Autodesk for $60 million in 2012 after 18 months. In 2014, Justin.tv was renamed Twitch Interactive and later that year sold to Amazon for $970 million.
Startup mentoring and Y Combinator
In 2008, Seibel was a key mentor to the co-founders of Airbnb and recommended them to Y Combinator. In 2013, he became a part-time partner at Y Combinator and, in October 2014, became the organization's first African-American partner. He became CEO of the Y Combinator Startup Accelerator in 2016. On March 15, 2024, Seibel announced on X that he was stepping down from his leadership role after eight years and would return to his original role as partner.
During his tenure, Seibel played a significant role in expanding Y Combinator's reach, launching global programs and online initiatives such as Startup School, which opened YC mentorship and resources to founders worldwide. He has been widely credited with increasing the number of Black and underrepresented founders in YC's accelerator, making diversity and access a central priority of the organization during his leadership.
Investments and board seats
Some of Seibel's personal startup investments include Cruise, Brex, Figma, Rippling, Reddit, Clipboard Health, and Promise. He is also a frequent speaker at major startup and technology conferences, including TechCrunch Disrupt, AfroTech, and Startup Grind, where he advocates for diversity, access to capital, and mentorship in tech entrepreneurship.
On June 10, 2020, it was announced that Seibel had been named to the Reddit board of directors, replacing Alexis Ohanian, who had resigned on June 5, 2020 in response to the murder of George Floyd and urged the board to fill his seat with a Black candidate. Reddit later named Seibel as the "first black board member in the company's history." On December 15, 2020, it was announced that Seibel was named to the Dropbox board of directors.
AI startup advising
As a partner at Y Combinator, Seibel has advised numerous startups working on machine learning and generative AI technologies. His guidance often focuses on practical product development and market fit, drawing on his experience with consumer platforms like Twitch and Socialcam. He has been particularly active in encouraging founders to build applications leveraging large language models, a growing area of interest within the accelerator's portfolio.
Seibel's approach to advising emphasizes the importance of founder resilience and clear communication, skills he honed during his own entrepreneurial ventures. He has also spoken about the potential of AI to transform various industries, while cautioning founders to focus on solving real user problems rather than chasing technological novelty.
Legacy and influence
Seibel's influence extends beyond individual startups. His leadership at Y Combinator helped shape the modern startup ecosystem, particularly in promoting diversity and global access. His board roles at Reddit and Dropbox reflect his standing as a trusted advisor in the technology community. As of 2024, he continues to serve as a partner at Y Combinator, where he remains a vocal advocate for underrepresented founders and a mentor to the next generation of entrepreneurs.