As a new type of two‐dimensional (2D) materials, monoelemental 2D materials have the atomic structure similar to graphene, and their excellent optical and electronic properties have potential applications in many fields. To date, many studies based on monoelemental 2D materials have been reported, and excellent performance has been demonstrated in various fields. The monoelemental 2D materials that have been reported so far are mainly distributed in the group IIIA, IVA, VA, and VIA. Because of their structural similarities to graphene, they are commonly referred to as "Xenes." Here, we have comprehensively reviewed the research progress of monoelemental 2D materials. In this review, we explore the structure, properties, and practical applications of these monoelemental 2D materials. First, the classification, structural features, optical properties, electronic characteristics, and regulating mechanism of these monoelemental 2D materials are introduced. Then, the practical application and research progress of monoelemental 2D materials in various fields are reviewed comprehensively, especially including photoelectric catalysis, solar cells, and other energy fields. This review will give readers a more all‐sided understanding of monoelemental 2D materials and have some guiding significance for their further development. Monoelemental 2D materials are mainly distributed in groups IIIA, IVA, VA, and VIA of the periodic table. Their adjustable optical and electronic properties make them have good application prospects in the fields of energy, optics, and optoelectronics.