This chapter describes the changing dynamics of regionalism and alliance-making in the Middle East, processes that are closely related to and reflect states' foreign and domestic policy choices. The Middle East is not a region without regionalism at the societal or interstate level. There have been multiple forces for cooperation, particularly in the Arab world, based upon common identity, interests and beliefs; multiple alliances that intersect the Arab and non-Arab world; and evidence of cooperation in both broader and narrower regional settings like the Gulf. Global as well as regional trends and influences also push the Middle East into new arenas of cooperation. However, outcomes are mixed: an array of factors including regime insecurity, local rivalries, and external influence inhibit attempts at regional cooperation. Events since the Arab Spring have presented opportunities but also further challenges for Arab regional institutions as new divides and regional alignments emerge.