The criminal statute of limitations is one of the important institutions of modern criminal law and is recognized as a mechanism for extinguishing the public claim or halting the execution of ta‘zir punishments. The present study, aiming to identify the theoretical foundations and practical effects of this institution in the two prominent legal systems of Iran (based on Imamiyyah jurisprudence and the Islamic Penal Code of 2013) and the United States (based on the common-law system, the Federal Constitution, and state legislation), has been conducted using a descriptive–analytical method and a comparative approach. The findings indicate that in the Iranian legal system, the statute of limitations is recognized solely for ta‘zir offenses and encompasses three categories: the limitation of complaint, limitation of prosecution, and limitation of enforcement of punishment (Articles 105 to 113 of the Islamic Penal Code). In contrast, in the United States, the criminal statute of limitations is primarily regulated at the state level and, as a rule, does not apply to serious federal crimes (such as intentional homicide, treason, terrorism, and genocide), but for lesser and mid-level offenses, it is set between 3 and 10 years (and sometimes longer). The most important similarity between the two systems is the decisive role of the prosecutor in initiating or terminating prosecution and the shared emphasis on “public interest” and “legal certainty.” The major differences include: (a) the jurisprudential–religious foundations in Iran versus the customary and case-law foundations in the United States; (b) the non-applicability of the statute of limitations to hudud, qisas, and diyat in Iran versus its non-applicability to most serious federal crimes in the United States; and (c) the comparatively longer judicial process in Iran, resulting in a greater impact of the statute of limitations on reducing case backlogs. The results of the study suggest that the institution of the criminal statute of limitations, while preserving the rights of the accused and preventing excessive delays in adjudication, can help reduce the prison population, increase the efficiency of the criminal justice system, and contribute to situational crime prevention. It is recommended that the Iranian legislature, inspired by the U.S. experience, expand the discretionary authority of prosecutors in applying the statute of limitations and adopt shorter limitation periods for minor economic and environmental offenses.