Over the past few decades, seaweed taxonomy has undergone substantial transformation, largely driven by molecular data that have reshaped our understanding of marine algal diversity and the processes underlying current biodiversity patterns. However, progress in documenting seaweed biodiversity remains geographically uneven, with several tropical regions still significantly understudied. This lack of baseline data on species diversity and distribution hinders efforts to fully understand tropical marine ecosystems. New findings are presented on seaweed diversity in the tropical Indo-Pacific, focusing on key taxonomic groups such as the green algae Ulva, Bryopsis, and members of the order Cladophorales, the red alga Portieria, and the brown algal order Dictyotales. Recent methodological advances, including the mining of short-read sequencing datasets to detect microscopic or previously overlooked lineages, have enhanced our capacity to uncover cryptic diversity. These studies underscore the pivotal role of molecular data in seaweed biodiversity studies, and highlight how diverse biological traits have contributed to biogeographical patterns in seaweeds. Given the disproportionate underrepresentation of tropical regions in seaweed biodiversity studies, I emphasize the need for international collaboration and equitable partnerships. Strengthening local expertise in taxonomy, collection management and digitization, biodiversity informatics, and molecular techniques is essential. Additionally, promoting the role of seaweed taxonomy in policy, conservation, and aquaculture, and encouraging community support for global biodiversity platforms will be critical for advancing our understanding of tropical marine biodiversity.