Using two novel datasets and a more comprehensive sample, we document a new stylized fact: tax havens play a major role in mergers and acquisitions (M&A). Cross-border M&A involving either an acquiror or a target from a haven accounts for 29.7% of cross-border M&A volume, or 11.1% of all M&A activity. We investigate 20,360 such transactions from 1990 to 2023, valued at $8.3 trillion. $4.6 of the $8.3 trillion is classified as “abnormal” activity based on a gravity model with economic fundamentals. Small havens alone account for $2.4 trillion, or 8.5% of cross-border M&A volume (e.g., Bermuda, the Cayman Islands).