This thesis examines to what extent International Relations (IR) Realist Theory explains the United States-Israel relationship. It studies the evolution of the United States-Israel relationship through the Cold War and post-Cold War period to analyze how it has developed to the one these two countries share today. The United States gives Israel robust economic, military and diplomatic support. This thesis argues that the benefits that the United States receives outweigh the costs of the relationship, and that supporting Israel helps achieve the United States' national interests of preserving stability and access to oil in the region.