With the discovery of graphene, a frenzy was set in motion to explore two-dimensional materials and its potential applications. In recent years, considerable efforts have been devoted to the demonstration of atomically-thin optical devices using graphene, transition metal dichalcogenides, and other two-dimensional(2D) materials. The combination of two-dimensional materials and flat-optics has yielded fruitful unexpected results. These ultra-thin two-dimensional optical devices can not only realize the functions of traditional diffractive lenses, but also show excellent optical modulability in the sub-wavelength range, which broadens the potential of future applications. In addition to the excellent physical properties (such as good ductility and flexible substrate compatibility) of 2D materials, their Fermi level can be further tuned by gate voltage, thus effectively modulating the optical properties without moving the optical components, which makes the 2D ultra-thin optical components superior in terms of tunability as compared to conventional devices. Besides, tunable liquid crystal lens has a mature development, and graphene oxide, transition metal disulfide and many other two-dimensional materials also possess stable liquid crystal phases. It is natual to pay attention to ultrathin liquid crystal lenses based on two-dimensional materials in order to achieve the flexible and responsive two-dimensional tunable lenses. The emergence of two-dimensional ultra-thin tunable optics has not only paved the development of the next generation of optics, but also provided new hope for further high integration of optical components. Therefore, this review focuses on ultrathin lenses made of two-dimensional materials, as it will briefly outline the recent progress of subwavelength optical lenses made of two-dimensional layered materials as well as two-dimensional liquid crystal 2D materials. Moreover, this review also introduces the potential application of such lenses, and gives an outlook of this emerging research field.