Jerry Yang has resigned from Yahoo Inc., the company he co-founded in 1995, effective immediately. In addition to no longer being on the board or having any other official Yahoo affiliations, Yang also resigned from the boards of Yahoo Japan Corp. and Alibaba Group Holding Ltd.

His decision comes shortly after Scott Thompson left PayPal to accept the position of chief executive officer at Yahoo.

In his letter to Yahoo board chairman Roy Bostock, Yang wrote: “My time at Yahoo, from its founding to the present, has encompassed some of the most exciting and rewarding experiences of my life. 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 (pictured) has been on the Yahoo board of directors since March 1995, with business cards that famously gave his title as Chief Yahoo. He also served as the company’s chief executive officer from June 2007 to January 2009. Yahoo went public in 1996.

Bostock thanked Yang on behalf of the board and expressed their best wishes in whatever he chooses to do next.

“Jerry Yang is a visionary and a pioneer, who has contributed enormously to Yahoo during his many years of service,” Bostock said in a statement. “It has been a pleasure to work with Jerry. His unique strategic insights have been invaluable. He has always remained focused on the best interests of Yahoo’s stakeholders, including shareholders, employees and more than 700 million users. And while I and the entire Board respect his decision, we will miss his remarkable perspective, vision and wise counsel.”

Thompson also released a statement of gratitude for Yang’s inimitable role in creating one of the world’s first Internet search methodologies and growing it into a media and advertising powerhouse. He said: “Jerry leaves behind a legacy of innovation and customer focus for this iconic brand, having shaped our culture by fostering a spirit of innovation that began 17 years ago and continues to grow even stronger today. Jerry has great confidence in the future of Yahoo, and I share his confidence in the enormous potential of Yahoo in the days ahead.”

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Photo by Flickr user Yodel Anecdotal/Yahoo blog, used under Creative Commons license