The ability to detect single photons in the mid-infrared spectral range (beyond 2 μm wavelength, photon energy below 0.62 eV) is the key to unlocking a range of emerging scientific applications, from remote sensing LIDAR, molecular spectroscopy, and powerful new approaches to dark matter detection. Conventional detector types, such as semiconductor single-photon avalanche diodes, lose sensitivity at such low photon energy. Superconducting materials, with a much lower characteristic energy gap, hold particular promise. In this Perspective, we focus on recent advances in superconducting nanowire single-photon detectors, which have recently extended single-photon sensitivity up to 29 μm (0.043 eV). We discuss the potential for future advances and strategies to overcome challenges to technological development.