Fluorenone molecular materials provide an excellent platform to engineer new materials that are very promising for photonic and optoelectronic applications, such as very efficient optical second harmonic (SHG) and terahertz (THz) generation, light emitting diodes, biomarkers, solar cells, and sensors. More recently, there have been a lot of research efforts dedicated towards the nonlinear optical (NLO) properties of these fluorenone materials because of their unique combination of chemical, structural, and optical properties. This review addresses the state of the art of this very interesting and potent class of molecular materials. In particular, the NLO susceptibilities, their potential for optical SHG and THz generation and their two‐photon luminescence properties and how to optimize these by rational design are reviewed. Flexibility and easiness of modification of their molecular properties combined with their structural polymorphism enable a variety of applications. Perspectives and future research directions for these fluorenone materials are also presented.