Contemporary transformations in legal relationships—particularly within informal, digital, and professional interactions—have increased situations in which individuals form reasonable and justifiable expectations based on the conduct, statements, or established practices of others. The violation of such expectations may result in harm, even in the absence of an explicit contractual obligation or fault in its traditional sense. This phenomenon challenges the adequacy of classical frameworks of civil liability.

This article adopts an analytical–descriptive approach to examine the concept of legitimate expectation and its role in establishing civil liability within modern legal relationships. It first clarifies the concept of legitimate expectation and distinguishes it from related notions, then explores the contexts in which it arises, including pre-contractual negotiations, digital interactions, and professional relationships. Subsequently, the elements of civil liability arising from the breach of legitimate expectation are analyzed, with particular attention to reliance-based causation, the role of fault, and the principle of foreseeability of harm.The findings indicate that the breach of legitimate expectation may function as an independent or supplementary basis for civil liability, with compensation primarily focused on reliance damages rather than expectancy interests. Furthermore, an examination of Iranian law reveals that despite the absence of explicit legislative recognition, legitimate expectation can be supported through a dynamic interpretation of general principles of civil liability and overarching legal doctrines. The article concludes by emphasizing the need for a coherent doctrinal framework to enhance the effectiveness and adaptability of civil liability in response to evolving legal relationships.