Mid-infrared (Mid-IR) silicon photonic integrated circuits have drawn considerable interest due to their remarkable applications. However, previous devices are typically designed on waveguide configurations with hundreds of nanometers in thickness, hindering their application in sensing. Here, we demonstrated a suspended nanomembrane silicon (SNS) microring resonator (MRR) at 3.27 μm wavelengths with a subwavelength grating coupler. Our experimental results show that the SNS MRR showcases a quality factor of ~3500 with a giant confinement factor of 0.89 and reduced thermal sensitivity of 0.07 nm/°C. The study opens a new avenue to developing mid-IR silicon devices for sensing applications.