This thesis tackles the legal corporate perspective of Mergers and Acquisitions. On the first hand, it describes the evolution of Mergers and Acquisitions throughout the History, and the evolving of its waves. On the second hand, it gives a separate definition for each, Mergers and Acquisitions, in the European Union and in the United States of America. On the third hand, this research cites all the legal sources that bind an M&A transaction, and the regulatory bodies who check its legality and its compliance with the law (in the EU and in the U.S). Besides it shows what are the motives behind such a transaction. On the fourth hand, the thesis tackles all the legal and financial details concerning an M&A process, from it's beginning to it's last stage. Finally, it holds a conclusion that analyses all the work from my personal perspective.