We report on the detection of single photons with λ = 8 µm using a superconducting hotelectron microbolometer. The sensing element is a titanium transition-edge sensor with a volume ~ 0.1 µm 3 fabricated on a silicon substrate. Poisson photon counting statistics including simultaneous detection of 3 photons was observed. The width of the photon-number peaks was 0.11 eV, 70% of the photon energy, at 50-100 mK. This achieved energy resolution is one of the best figures reported so far for superconducting devices. Such devices can be suitable for singlephoton calorimetric spectroscopy throughout the mid-infrared and even the far-infrared.