This study is aimed at shedding light on this important and vital topic in the context of the fundamental changes experienced by the world of today, particularly in terms of liberation of world trade, the trend towards regional and economic blocks and the accompanying processes of companies merger. The study is divided into three chapters preceded by an introductory chapter focusing on definition of merger and its types. The three other chapters tackle the issues relating to merger. The study involves comparison between merger process in Oman's Commercial Companies Law and the laws of pioneer countries in this respect in order to make use of their legal experience so as to arrive at the optimum solution through research in merger of companies. I tried to tackle most of the legal aspects relating to the merger process as an important means of economic concentration. These aspects include reasons and forms of merger as well as its objectives, characteristics, terms and stages. The research also involves the procedures to be followed in order to complete the merger process, the difficulties encountered and the proposed solutions. The study is ended with a manifestation of the effects of merger. The study arrived at a number of recommendations which may play a role in the development of the Commercial Companies Law.