Abstract: Converting solar energy into storable and transportable chemical fuels through artificial photosynthesis represents one of the most promising solutions to address the global energy crisis and environmental issues. The key to realize artificial photosynthesis is to develop low-cost, efficient, and durable photocatalysts which can be synthesized in large scale. Recently, semiconducting polymers have emerged as a new class of photocatalysts for various photocatalytic applications as their electronic structures can be conveniently designed and controlled at a molecular level. Moreover, due to the unique two-dimensional (2D) planar structure, 2D polymer nanosheets stand out as the most intriguing polymeric materials for photocatalytic energy conversion. Compared to polymer photocatalysts with other dimensions, the 2D structure offers many distinct features such as high surface areas, abundant surface active sites, efficient charge separation, and facile formation of heterostructures with other materials. Here, recent progress in developing 2D polymers for photocatalytic overall water splitting is highlighted. Several approaches for tuning their electronic structures and surface active sites to achieve overall water splitting are introduced. It is expected that the design principles, synthetic methods, fabrication strategies, and characterization methodologies summarized here would be of great value for future solar energy conversion using polymer photocatalysts in light of that photocatalytic overall water splitting is not only fundamentally important in basic science but also critical for artificial photosynthesis. Meanwhile, future opportunities and challenges in developing polymer photocatalysts for water splitting are also pointed out. This report would stimulate further interests and efforts in developing polymers for solar-to-chemical energy conversion.