The Xiamen Symposium on Marine Environmental Sciences 2025 (XMAS 2025) will be held from January 14th to 17th, 2025 in Xiamen, China. It is organized by the State Key Laboratory of Marine Environmental Science, Xiamen University. Furthermore, for the first time, the symposium will be sponsored by the Association for the Sciences of Limnology and Oceanography (ASLO). XMAS 2025 will consist of interdisciplinary cutting-edged sessions covering physical, chemical, and biological oceanography as well as marine toxicology. In addition, workshops on emerging topics in marine environmental sciences such as ocean-based carbon removal, ocean governance and sustainability, the marine economy, marine education and outreach, and special sessions on Women in Science and mentoring future scientists will also be offered. All of these will feature ASLO members in addition to experts in these respective fields from around the world.