As the Syrian revolution enters its third year, the risks to regional stability are escalating. Violence has spilled over all of Syria's borders. The conflict has elevated sectarian tensions in Lebanon, threatening the 1990 Taif settlement that ended 15 years of civil war. It has sharpened ethnic and sectarian frictions in Iraq and engulfed southern Turkey. It has heightened tensions across the Syrian-Israeli border. Violence has also spilled into Syria from across the region. Regional involvement in the conflict is deepening. Syrian refugees, now numbering more than a million, are straining the economies and the social fabric of receiving countries. This paper addresses the implications of the regionalisation of Syria’s conflict and the challenges it presents to the stability of the post-Ottoman state order in the Levant.