Mr Icahn wanted to force through the sale of Yahoo to Microsoft
Billionaire investor Carl Icahn has resigned with immediate effect from the board of internet giant Yahoo.
Mr Icahn said he thought the company no longer needed an activist investor as a director, and his attention was now "focused on other matters".
Mr Icahn was involved in a very public dispute last year with Yahoo co-founder Jerry Yang over the proposed sale of the company to Microsoft.
Earlier this week, Yahoo said its third quarter profits more than trebled.
The company said it earned $186m (£114m) between July and September compared with $54m in the same period last year.
Last July, Yahoo reached an agreement with Mr Icahn to stop him attempting to replace its board.
Mr Icahn was annoyed that Yahoo had resisted Microsoft's attempts to take it over, and wanted to force through a sale.
Under the terms of the deal, Yahoo's board was expanded from nine to 11 members, comprising Mr Icahn and two of his nominees, along with eight of the original members.
The sale was never agreed, but in July this year, the two companies did strike a deal, whereby Microsoft's Bing search engine would power the Yahoo website, and Yahoo would become the advertising sales team for Microsoft's online offering.