Due to its unique gate-tunable non-volatility, the memtransistor is a promising component for low-energy neuromorphic computing. The grain boundary- and point defect-enabled resistive switching in MoS₂ memtransistors suggests an inherent ionizing radiation tolerance. However, the memtransistor resilience under heavy ion irradiation has not yet been investigated. In this work, polycrystalline, monolayer MoS₂ films, and memtransistors are irradiated with 48 keV Au. Fluence-dependent effects on the MoS₂ lattice structure, chemical states, and memtransistor performance metrics are elucidated. When the Au fluence remains below 10¹³ cm⁻², the memtransistor functionalities are preserved. When the Au fluence exceeds 10¹⁴ cm⁻², the MoS₂ is amorphized and memtransistor functionalities are lost. According to Raman spectroscopy and transmission electron microscopy, the MoS₂ defect concentration increases with increasing Au fluence. X-ray photoelectron spectroscopy substantiates a significant S:Mo ratio reduction with increasing Au fluence. This work suggests that MoS₂ memtransistors possess sufficient heavy ion resilience for few-year space missions.