The accumulation and fragmentation of plastic debris in global environments are significant environmental issues. Since the mass production of plastics began in the 1950s, plastic waste has spread across terrestrial environments, the open ocean, shorelines, and even remote islands and deep seas. Annual clean-up operations are now organized in many countries and continents, costing millions of pounds. Plastics typically constitute about 10% of discarded waste but represent a much larger proportion of debris on shorelines. Mega- and macro-plastics are most abundant in the Northern Hemisphere near urban centers, enclosed seas, and water convergences, while remote island shores, continental shelves, and the deep sea have lower densities. The longevity of plastic debris is estimated to be hundreds to thousands of years, but it may be longer in deep sea and polar environments. Plastic debris poses threats such as choking wildlife, distributing non-native species, absorbing toxic chemicals, and degrading into micro-plastics. Trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing but vary, with stable, increasing, and decreasing trends reported. The average size of plastic particles is decreasing, and the abundance and distribution of micro-plastics have increased over the last few decades. However, the environmental consequences of micro-plastics are still poorly understood.The accumulation and fragmentation of plastic debris in global environments are significant environmental issues. Since the mass production of plastics began in the 1950s, plastic waste has spread across terrestrial environments, the open ocean, shorelines, and even remote islands and deep seas. Annual clean-up operations are now organized in many countries and continents, costing millions of pounds. Plastics typically constitute about 10% of discarded waste but represent a much larger proportion of debris on shorelines. Mega- and macro-plastics are most abundant in the Northern Hemisphere near urban centers, enclosed seas, and water convergences, while remote island shores, continental shelves, and the deep sea have lower densities. The longevity of plastic debris is estimated to be hundreds to thousands of years, but it may be longer in deep sea and polar environments. Plastic debris poses threats such as choking wildlife, distributing non-native species, absorbing toxic chemicals, and degrading into micro-plastics. Trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing but vary, with stable, increasing, and decreasing trends reported. The average size of plastic particles is decreasing, and the abundance and distribution of micro-plastics have increased over the last few decades. However, the environmental consequences of micro-plastics are still poorly understood.