There are 28 federal states in the world, including Iraq, which implemented two federal experiments. The first experiment was between the two Hashemite monarchies in Iraq and Jordan in 1958, while the second experiment was implemented within the framework of the new Iraqi political system that was established after 2003.There is no doubt that the external factor was influential in both experiments, which confirmed the lack of popular satisfaction in general, which led to the rapid collapse of the Arab Union, and confront the Iraqi federal system a lot of challenges and problemsThis research seeks to answer the following question: Were the federal applications in Iraq a popular or governmental will, and whether they had similar or different elements?This research was divided into two sections. The first topic dealt with the Arab Union, which was established in 1958, while the second topic dealt with the federal system which was established in 2004.The most important conclusions reached in this research are:1-Difficult to classify the type of Arab Union, the opinions were distributed among this Union Confederation or a real union or personal union. It may be from two states and lasted about six months. Most of the legislative and executive powers were concentrated in the President of the Union.2-The federal system in Iraq was established constitutionally after 2003, by transforming the form of the Iraqi state from a simple unified to a federal. In spite of the distribution of the individual and joint competencies of each bodies of the federal state authority and the Kurdistan region and the provinces, but did not prevent interference in the terms of reference. This union has been going on since 14 years