Quasi-two-dimensional (quasi-2D) lead halide perovskite materials have shown great potential as gain media for amplified spontaneous emission (ASE) and lasing. Due to the complexity of the mixed-dimensional perovskite materials, factors influencing their ASE thresholds remain unclear, limiting the pace of development in this emerging area of research. Here, we report exceptionally low ASE thresholds of ∼2.23 μJ cm