The resignation was effective immediately.
"My time at Yahoo!, from its founding to the present, has encompassed some of the most exciting and rewarding experiences of my life," Yang said in his resignation letter. "However, the time has come for me to pursue other interests outside of Yahoo! As I leave the company I co-founded nearly 17 years ago, I am enthusiastic about the appointment of Scott Thompson as chief executive officer and his ability, along with the entire Yahoo! leadership team, to guide Yahoo! into an exciting and successful future."
Yang, a 43-year-old immigrant from Taiwan, co-founded the digital media company with David Filo in 1995 and has been a board member since March of that year, serving as chief executive officer from June 2007 to January 2009.