Organometal halide perovskites (OHPs) exhibit extraordinary properties in the emulation of synaptic plasticity in artificial synaptic electronic devices. However, the instability of OHPs has hindered their further application. Here, a novel two-terminal artificial synapse based on two-dimensional perovskite (R-MPEA)1.5PbBr3.5(DMSO)0.5 was developed to address this challenge. Essential biological functions including excitatory post-synaptic current, paired-pulse facilitation, spike-number dependent plasticity, spike-voltage dependent plasticity, spike-duration dependent plasticity, and spike-rate dependent plasticity, have been demonstrated in OHP-based synaptic devices. More importantly, this is the first demonstration of an air-stable OHP-based artificial synapse. The OHP-based synaptic device achieved extremely low energy consumption (∼21 fJ per event) in short-term memory and exhibited good stability at ambient atmosphere over 300 h. These results may open a new avenue for next-generation synaptic electronics and neuromorphic computing. [ABSTRACT FROM AUTHOR]