The paper explores the formation of primordial black holes (PBHs) from the collapse of axion domain walls. Axions, a solution to the Strong CP Problem and potential dark matter candidates, can form strings and domain walls during the early universe. These walls can collapse, compressing a large amount of energy into a small volume and potentially forming PBHs. The authors study the number density and dynamics of self-enclosed walls, considering their size distribution, Hubble expansion, asphericities, and all stages of domain wall dynamics using semi-analytic and numerical approaches. They find that axion models with high decay constants, such as those relevant in early matter-dominated cosmologies, can yield a PBH abundance detectable by future gravitational lensing surveys. The formalism developed is also useful for predicting relic PBH abundances in other models with unstable domain walls. The paper covers topics including the overview of axion cosmology and topological defects, the abundance and dynamics of closed domain walls, the superhorizon and subhorizon expansion of domain walls, the conditions for PBH formation, and the abundance and detection prospects of PBHs.The paper explores the formation of primordial black holes (PBHs) from the collapse of axion domain walls. Axions, a solution to the Strong CP Problem and potential dark matter candidates, can form strings and domain walls during the early universe. These walls can collapse, compressing a large amount of energy into a small volume and potentially forming PBHs. The authors study the number density and dynamics of self-enclosed walls, considering their size distribution, Hubble expansion, asphericities, and all stages of domain wall dynamics using semi-analytic and numerical approaches. They find that axion models with high decay constants, such as those relevant in early matter-dominated cosmologies, can yield a PBH abundance detectable by future gravitational lensing surveys. The formalism developed is also useful for predicting relic PBH abundances in other models with unstable domain walls. The paper covers topics including the overview of axion cosmology and topological defects, the abundance and dynamics of closed domain walls, the superhorizon and subhorizon expansion of domain walls, the conditions for PBH formation, and the abundance and detection prospects of PBHs.