The Marine Debris Monitoring Methods Handbook, Part 1 (this handbook) seeks to provide information to participants in COBSEA participating countries about the different monitoring approaches that are taken in international marine litter monitoring programs. The objective of this handbook is to provide a menu of options that have been rolled out at national and multinational/regional scales to monitor marine litter, to provide guidance on best-practice in marine litter monitoring approaches for regional-scale marine litter monitoring.