This training on marine litter monitoring and assessment was developed in partnership with the Commonwealth Scientific and Industrial Research Organisation (CSIRO). It enables course participants to establish/design a programme to monitor and assess the distribution and abundance of plastic litter to support national monitoring programmes. Training material is designed to support hybrid trainings with a 2-part handbook and video modules to introduce monitoring and established methods for surveys in different habitats, building on COBSEA Regional Guidance on Harmonized National Marine Litter Monitoring and global guidelines.