The controlled coupling of photon emitters with tailored nanophotonic structures offers an exciting platform for studying fundamental quantum electrodynamics (QED) and developing on-chip quantum information processing at telecom-compatible wavelengths. Here we introduce a three-dimensional polariton waveguide structure, capable of achieving strong coupling with a single quantum emitter. This polariton waveguide consists of a nanowire-based photonic crystal (PC) waveguide with a quantum dot (QD) embedded in each unit cell. Using realistic designs and parameters, we derive and calculate the fundamental electromagnetic properties of these polariton waveguides, with an emphasis on the local optical density of states (LDOS) and the photon Green function. We demonstrate dramatic increases, and rich fundamental control, of the LDOS due to strong light–matter interactions in each unit cell through periodic QD interactions and further show that these results are quite robust to structural disorder. As an example application, we consider the coupling of an external target QD with a finite-sized polariton waveguide, and show that the single QD strong coupling regime is easily accessible, even for modest dipole strengths. Our polaronic structures are fundamentally interesting and allow for the exploration of new regimes of waveguide QED. While our calculations are exemplified for a PC nanowire system, the general results apply to a wide range of PC waveguides including planar PC slabs and “alligator” PCs, as well as circuit-QED systems.