Emulation of memory and learning functionalities of biological synapses using a two-terminal electronic device with bidirectional progressive conductance modulation is an indispensable move toward the development of bio-inspired neuromorphic networks. Herein, a small molecule 1-phenyl-2-(4-(pyren-1-yl) phenyl)-1H-phenanthro[9,10-d]imidazole (pPPI) is synthesized, and an organic synaptic device is investigated with bipolar resistive switching characteristics and bidirectional gradual conductance regulation for the first time. A facile solution-processing approach can be used to deposit a uniform active layer on flexible substrates. Our pPPI-based nonvolatile memory presents a superior electrical performance, such as relatively stable and reproducible bipolar resistive switching phenomena and a robust data retention capability. In particular, our device displays a remarkably large switching window of around 7.0 Â 10 7 , which is a record ON/OFF ratio compared with other small molecule-based memories up to now. In addition, comprehensive cognitive functions of chemical synapses, for example, the excitatory postsynaptic current (EPSC), paired-pulse facilitation/depression (PPF/PPD), spike-rate-dependent plasticity (SRDP), and spike-time-dependent plasticity (STDP) are successfully achieved. Our achievement of a synaptic device based on small molecules may boost the development of bio-inspired neuromorphic systems using organic electronics.