Hybrid perovskites are solution processed crystalline materials with excellent electronic and optical properties, which enables high-efficiency optoelectronic devices. However, hybrid perovskites-based field effect transistor operation at room temperature has remained elusive. This is due to the non-reproducibility induced by polar nature of the structure coupled with ionic motions, which screens the capacitively coupled gate voltage. In this study, we report high-performance, hysteresis-free ambipolar FETs using highly crystalline hybrid perovskites thin films, operating at room temperature. We systematically improved the film quality, the effect of high-K dielectrics between the perovskites and gate. As a result, we obtained FETs with high trans-conductance with low subthreshold slopes leading to an on/off ration >104. Moreover, we achieve ambipolar transport at room temperature that strongly correlates to the choice of the gate-dielectric, that allow to tune the Fermi energy of perovskites for electrons and holes injections. We anticipate these results will open up the systematic investigation on the electronic properties in hybrid perovskites materials, for the opportunities to discover novel devices functionalities such as ultrasensitive photo-transistors and spin FETs.