The emergence in December 2019 of SARS-CoV-2, and its infectious disease COVID-19, has resulted in a worldwide pandemic. Despite the realization that humanity is under a constant threat from respiratory viruses with pandemic potential, such as coronaviruses and influenza viruses, the discovery of a safe and effective prophylactic drug against such infections has remained elusive. The benefits of such a drug for the prevention, containment, or mitigation of emerging and endemic viral threats would be significant. As research on the mechanisms of viral infection has advanced, the repositioning and repurposing of existing drugs and therapeutics has played a significant role in our attempts to find efficacious treatments. This is especially true for COVID-19, though numerous existing drugs were previously studied for their usefulness in treating both SARS-CoV and MERS-CoV infections. Ambroxol, a semi-synthetic derivative of the alkaloid vasicine, has been researched and marketed for more than half a century. Ambroxol was originally marketed as a respiratory mucolytic, mucokinetic, expectorant, and secretolytic. Decades of research have shown it to possess multiple effects, with minimal side effects and a favorable safety profile. Among the mechanisms of action and molecular targets that have been shown for Ambroxol, some of these are potentially of benefit for the prevention and treatment of viral infections caused by influenza viruses, rhinoviruses, and coronaviruses. If proven to be safe and effective, the repurposing of Ambroxol as a phylactic and treatment for these viral infections would be a major advancement in public health, by lowering the morbidity and mortality caused by these viruses.