"Dear Board letter" is a letter from an activist investor to the board of a company, in which the investor attempts to persuade the board to make certain sweeping decisions. The letter is usually a formal starting point to put pressure on the board and gets its name from the salutation, which often begins with "Dear Mr. CEO..." or "Dear members of the Board of Directors...."

Before the letter is sent, the investor has often already built up an equity position and conducted a thorough analysis of the company. Also, one-on-one discussions with the board may have already taken place. If these discussions do not lead to the desired action, the Dear Board letter is sent to put the demands on the table and to put certain issues on the agenda of the general meeting of shareholders (AGM).

The activist investor often seeks supporters early on to reinforce his plans. If the board does not respond, the pressure is further increased through critical statements in the press, social media, or even by initiating legal proceedings.