The doctrine of fundamental change of contractual circumstances is one of the modern legal mechanisms designed to preserve contractual balance in the event of unforeseen incidents beyond the control of the parties. This study aims to conduct a comparative analysis of this doctrine in Iranian and Egyptian law, with reference to the 2016 amendments to the French Civil Code, and to examine the potential for its integration into the Iranian legal system. The research adopts a combined comparative approach, assessing the theoretical foundations, conditions for application, legal consequences, and the role of party autonomy in all three systems in parallel rather than in isolation. The findings indicate that, while Iranian law lacks an explicit statutory provision to address fundamental changes in circumstances, Islamic legal maxims such as lā ḍarar (no harm) and nafī al-ʿusr wa al-ḥaraj (elimination of undue hardship), along with the general principles of the Civil Code, provide a basis for recognising contractual adjustment mechanisms. In Egyptian law, Article 147 of the Civil Code—drawing on Islamic jurisprudence and inspired by the pre‑2016 French model—provides a . The 2016 reform of French law, through the adoption of Article 1195 and the requirement of renegotiation, marks a significant move towards alignment with international instruments and the theory of contractual justice. The study concludes that a hybrid model combining the procedural flexibility of the French approach with the legislative clarity of the Egyptian framework, underpinned by Iranian fiqh principles, could fill the current legislative gap and strengthen contractual justice in Iran.