Hybrid organic–inorganic lead halide perovskite microwires are potential building blocks for realizing on-chip integrated optoelectronic devices. However, the length-controllable synthesis of one-dimensional hybrid perovskite microwires has been rarely reported, especially the ones with lengths in the millimeter scale. Herein, methylammonium lead bromide (MAPbBr3) and formamidinium lead bromide (FAPbBr3) micro and milliwires are demonstrated using single-crystal PbBr2 microwires synthesized via template-free solution-phase growth as the lattice framework. Following the PbBr2 template, the as-converted perovskite microwires possess controllable lengths ranging from tens to thousands of micrometers. In addition, Fabry–Perot (FP) lasing was realized in both MAPbBr3 and FAPbBr3 microwires, attesting to their excellent crystal quality and the efficient optical confinement of the natural cavity. These unique properties result in the first demonstration of FP perovskite microwire lasers with submillimeter lengths. More interestingly, the microwire lasers show excellent photostability under repetitive pulsed laser excitation for over 8 × 106 cycles. Such findings demonstrate that the solution-converted hybrid lead bromide microwires have excellent optoelectronic performances promising for practical applications, and the size controllability indicates that this novel fabrication process may be feasible for large-scale industrial production.