Squeezing photon energy into a deep subwavelength scale opens the path to strong light–matter interactions and has been extensively studied in plasmonics. Numerous applications have been demonstrated using noble metals and plasmonic graphene, which include waveguiding,1–3 refractive index sensing,4–6 perfect absorption,5,7,8 and Purcell factor enhancement,9,10 to name but a few. However, in the mid-infrared (mid-IR) spectral range, plasmonic materials suffer from either lack of confinement of the plasmon wave (in the case of noble metals) or high optical loss (in the case of graphene), which limit their practical applications. Recent advances in mid-IR phononic technologies provide an effective approach to address these challenges by using polar crystals as an alternative low-loss platform for highly integrated photonics. Such materials enable extremely confined phonon polaritons that exhibit lifetimes one order higher than almost all plasmonic counterparts.