English summary: In the years 1165-1178, religious and political Byzantine and Armenian authorities were in constant contact in order to reach an agreement between the two Churches. Many letters were exchanged, partly in the Armenian language, that were preserved and compiled in a book by Nerses Lambronac"i. This book is an annotated translation of these texts, nineteen letters in all, considering the theological questions debated, but also providing important information on the historical situation. In addition to this central element, appendices include translations of three important documents for the study of the Armenian-Byzantine controversy in the twelfth century, a pamphlet by Nerses Lambronac"i, the anonymous narrative of the visit of Nerses Constantinople in 1197, and a writing on the Catholicos life of Nerses Schnorhali, one of the main protagonists, together with the Emperor Manuel Comnenus, of the Greek-Armenian religious reconciliation. French text. French description: Dans les annees 1165-1178, les autorites religieuses et politiques byzantines et armeniennes entrent en contact de maniere soutenue, dans le but de trouver un accord entre les deux Eglises. De nombreuses missives sont alors echangees, missives qui ont ete conservees pour partie en langue armenienne et compilees dans un recueil par Nerses Lambronac"i. Le present ouvrage est une traduction commentee de ces textes, dix-neuf lettres au total, qui envisagent les questions theologiques debattues, mais apportent egalement des informations importantes sur le plan historique. A cet element central s"ajoutent, en annexes, les traductions de trois documents importants pour l"etude de la controverse armeno-byzantine au XIIe siecle, un opuscule de Nerses Lambronac"i, le recit anonyme de la visite de ce meme Nerses a Constantinople en 1197, et une Vie du catholicos Nerses Snorhali, l"un des principaux protagonistes, avec l"empereur Manuel Comnene, du rapprochement religieux armeno-grec.