A management buy-in or MBI transaction is a corporate finance event where an external team of managers acquires a controlling equity stake in a target company and replaces the incumbent executive leadership team to take over day-to-day operations. This differs from a management buyout, where the existing internal managers purchase the business. MBI transactions typically occur when a company underperforms or requires fresh strategic direction, bringing in experienced outside leaders to drive operational turnarounds and long-term value creation.