Michael Seibel

Michael Seibel, born October 7, 1982, in Brooklyn, New York, is an American entrepreneur and investor best known for his work in the startup accelerator Y Combinator. He co-founded the live-video company Justin.tv, serving as its chief executive from 2007 to 2011; the company later pivoted into Twitch, the game-streaming service Amazon acquired in 2014. He also co-founded the video-sharing app Socialcam, which Autodesk bought in 2012.

Seibel joined Y Combinator as a part-time partner in 2013 and, in October 2014, became the accelerator's first African-American partner. He went on to lead Y Combinator's core startup accelerator program as chief executive from 2016 until stepping back to a partner role in 2024. Y Combinator's first 2005 batch had included Reddit, giving Seibel a longstanding connection to the company's earliest backers and to investor Sam Altman.

On June 10, 2020, Reddit named Seibel to its board of directors, describing him as the first Black board member in the company's history. The appointment came days after co-founder Alexis Ohanian publicly resigned his board seat on June 5, 2020, in the wake of the murder of George Floyd, urging the board to fill the vacancy with a Black candidate. The episode was widely covered as a notable instance of a tech board responding directly to a public call for representation.

Reporting at the time framed Seibel's addition both as a substantive governance change and as part of a broader reckoning over diversity in technology leadership during 2020. As an accelerator partner with a portfolio spanning numerous prominent startups, Seibel brought operator and investor experience to a board that was, in the years that followed, steering Reddit toward its March 2024 initial public offering. He has continued to be cited in coverage of Reddit's governance and of Y Combinator's role in shaping early-stage technology companies.