We study the stability conditions for resonant cavities with spherical mirrors made from graded‐index (GRIN) rods. The spherical mirror is made by putting a high‐reflective (HR) coating on one of the flat ends of a GRIN rod segment. It is shown that one or two GRIN mirrors can be used to make all the usual resonator configurations. In particular, two GRIN mirrors attached to a solid‐state dielectric laser rod can be substituted for curved mirrors ground on the rod ends; the ends need only be reasonably flat. We present the following experimental verification: (i) The cw operation of a resonant cavity consisting of a flat/flat Nd : YAG rod with a GRIN mirror attached to one end, and (ii) the construction and operation of anarrayof GRIN mirrors which defines several independent simultaneously oscillating resonators within a single flat/flat Nd : YAG rod. We suggest the possibility of building a compact array of many closely packed miniature resonators by cementing a large number of GRIN mirrors to the top of a 5‐mm‐thick Nd : YAG disk, the bottom of which is HR coated. The disk can be diode pumped through the circumference and/or the bottom.