The Global Estuaries Monitoring (GEM) Programme (https://www.globalestuaries.org), proposed to the UNESCO Intergovernmental Oceanographic Commission in 2021 and endorsed as one of the first group of Ocean Decade Programs by the United Nations Decade of Ocean Science for Sustainable Development (2021–2030), has made significant strides over the past five years of operation. The GEM Programme’s primary objective is to establish standardized methodologies for sampling, extraction, detection, and quantification of priority chemical contaminants in samples from major urbanized estuaries globally. These standardized procedures will facilitate robust comparisons of contamination profiles across diverse estuarine ecosystems. Since the commencement of the first phase sampling initiative in July 2023, 187 estuaries have been sampled across 51 countries/regions. Notably, 60 estuaries were sampled during both dry and wet seasons, enabling a temporal analysis of contamination dynamics. The first phase of sampling was concluded by the end of 2024, paving the way for the second phase of research in mid-2026. In the upcoming phase, the GEM Programme will expand its monitoring capabilities by deploying innovative passive samplers developed by the GEM Team in estuaries worldwide, facilitating broader surveillance of emerging chemical contaminants. Through its research efforts, the GEM Programme aims to illuminate the global pollution landscape and advocate for best practices to combat environmental degradation, ultimately fostering cleaner and healthier estuaries for a sustainable and greener future.