Abstract: Ultrathin Fresnel lens may revolutionize current optical imaging system, leading to thinner and lighter optoelectronic devices with a myriad of technical applications. To date, evaporated bulk metal films and top-down grown graphene represent viable material choices toward the design of ultrathin Fresnel lenses. Despite recent advances, it is still lack of a scalable fabrication strategy to achieve ultrathin lens with high focusing efficiency. Here, we report a new self-assembled metamaterials-based strategy to design ultrathin Fresnel lens using our recently reported plasmene nanosheets. With comparable thickness, our plasmene-based Fresnel lens offers a much better focusing efficiency than that based on continuous metallic films. This may be attributed to the dual Huygens effects from both slits and plasmene-constituent nanoparticle building blocks. Importantly, internal structural features of plasmene can be precisely tuned simply by adjusting sizes and shapes of its constituent building blocks, allowing for maximizing the focusing efficiency at a desired operating wavelength a capability impossible to achieve with continuous metal films or graphene. Our plasmene-based strategy opens a new route to design tailor-made flat lens with finely tunable internal and overall structural properties, which offers new dimensionalities in controlling light-matter interactions for a myriad of technological applications.