Magnesium (Mg) alloys are used for medical implants that gradually dissolve and safely absorb into the human body after healing. Complete dissolution eliminates the need for a second surgical intervention for implant removal, thereby reducing additional trauma and recovery time of the patient. Rapid corrosion rates of Mg alloys in body fluids and their susceptibility to mechanical loading in the case of load-bearing implants are the main reasons limiting the widespread use of Mg alloys as a biodegradable material. The concurrence of mechanical loading and an aggressive environment, such as body fluid, dramatically accelerates the dissolution rate and leads to premature implant failures with life-threatening consequences. A phase-field model is developed to simulate the corrosion of bioabsorbable metals in environments that resemble biological fluids. The framework captures pitting (localized) corrosion and incorporates the role of mechanical fields in enhancing the corrosion of biodegradable metals. The model is validated against in vitro corrosion data on Mg alloys immersed in simulated body fluid. The potential of the model to capture mechano-chemical effects is demonstrated in representative case studies considering Mg wires in tension and bioabsorbable coronary stents subjected to mechanical loading. The results show that pitting severely compromises the structural integrity of the stent and the application of mechanical loading initiates a pit-to-crack transition and crack propagation, leading to premature fracture after a short time in solution. This work extends phase-field modeling to bioengineering and provides a novel mechanistic tool for assessing the service life of bioabsorbable metallic biomedical devices.