Global warming is a critical issue that cannot be ignored, especially its impact on marine ecosystems. Rising sea temperatures are one of the direct effects of global warming. This increase in temperature causes stress in various marine species, triggering changes in the behavior, reproduction and migration patterns of fish and other marine organisms. In the long term, this has the potential to change the species composition and biodiversity in marine habitats. One of the significant impacts of global warming is ocean acidification. The absorption of carbon dioxide (CO2) from the atmosphere by the ocean produces carbonic acid, which reduces the pH of seawater. This has a big impact on organisms that have calcium skeletons, such as coral reefs, molluscs and some plankton. Ocean acidification can inhibit the process of calcium carbonate formation, causing weak coral reef fragments and reducing the survival of species that depend on reefs as habitat. Coral reefs themselves are very vulnerable to temperature changes and acidification. When ocean temperatures are too high, a process called coral bleaching can occur. In this condition, coral reefs emit symbiotic algae that provide color and nutrition, causing mass death of coral reefs. Frequent bleaching will affect the entire surrounding ecosystem, reducing habitat for fish and other sea creatures. In addition, changes in rainfall and polarization of marine ecosystems due to global warming can trigger eutrophication phenomena. Increased rain can increase the flow of nutrients, such as nitrogen and phosphorus, into the ocean. This causes excessive algae growth, which can result in dead zones. Dead zones refer to areas where oxygen levels are very low, making it difficult for marine organisms to survive. Species migration rates are also affected by global warming. Many fish species, for example, move to cooler or deeper areas in search of comfortable temperatures. This movement causes changes in population structure, affecting fisheries activities and the food security of communities that depend on marine resources. Changes in wind patterns and ocean currents due to global warming should not be ignored. Changing ocean currents can affect the circulation of nutrients in the ocean, damaging ecosystems that have existed for thousands of years. Not only that, the impact of extreme weather such as stronger tropical storms also threatens the sustainability of maritime habitats and the humans who depend on them. Based on data from various studies, it is important for countries around the world to take significant action to reduce carbon emissions. Conservation efforts, sustainable management and protection of marine ecosystems must be a priority to mitigate the impacts of global warming. In this way, we can maintain the balance of the marine ecosystem which is vital for our planet and future generations.