An activist investor is a shareholder who uses their ownership stake in a company to influence its management and operations. These investors typically buy a significant number of shares to gain enough power to push for changes that they believe will increase the company's value. Their strategies may include advocating for restructuring, changes in leadership, or alterations in business strategy. Activist investors often target companies that they perceive as underperforming or mismanaged. They may engage in public campaigns, propose new policies, or even seek seats on the board of directors. Notable examples of activist investors include Carl Icahn and Bill Ackman, who have made headlines for their high-profile interventions in various companies.