The Mekong River sustains a rich tapestry of fish species crucial for the well-being, food security, and livelihoods of millions in the region. However, these vital creatures face escalating threats, with one in five already endangered. A report by 25 organizations unveils the staggering diversity of the Mekong's fish, numbering at least 1,148 species and comprising the third most biodiverse river ecosystem globally. From giants to minnows, the Mekong hosts an astonishing array of fish life, including one of Earth's largest animal migrations, totaling around 5 billion individuals. This unprecedented report underscores the indispensable role these fish play in maintaining the river's health, sustaining economies, and ensuring the food security of over 40 million people who depend on the Mekong's inland fishery, generating over US$11 billion annually.