With the increase of energy crisis and greenhouse effect, the development of new photocatalytic systems with efficient solar-driven fuels/chemicals production is of great practical and scientific importance. In this scenario, single atom photocatalytic (SAP) systems are considered a significant breakthrough in the development of heterogeneous photocatalysis due to their superior catalytic efficiency, large surface area, and high atomic utilization. SAPs are consisting of isolated single atoms (SAs) distributed on/or coordinated with surface atoms of a suitable support. The anchoring of SAs on 2D substrates endows the developed SAPs with excellent properties, including high loading, uniform coordination, high light harvesting capability, and enhanced photocatalytic activities. Recently, many 2D substrates, including carbon materials, MXenes, and transition metal chalcogenides, have been used to anchor metal SAs for different photocatalytic applications. This review systematically discusses SAPs and the confining of metal SAs on 2D supports. Moreover, this review highlights the recent advances of SAPs for energy conversion, the existing challenges, and future perspectives. We expect that this review will offer some ideas for the future discovery of novel photocatalytic systems.