Belgium has often been considered as an example of a stable country characterized by consociational politics, heavy pillarization and a party system dominated by cleavage-based parties. Over the last decade, Belgium witnessed important changes and events that reshaped its institutional, electoral and societal structures. This chapter aims to investigate the challenges Belgium has faced that have strongly impacted its party system since the 2000s. The revival of the institutional conflict between French- and Dutch-speaking parties threatened the dominance of mainstream parties and led to the re-emergence of strong regionalist parties. In addition, the economic crisis and growing anti-establishment sentiment among large portions of the population fostered the rise of parties at the periphery of the party system, mostly radical-left and right-wing populist parties. More recently, the terrorist attacks in Brussels and the wave of political scandals put further pressure on the established parties. Along with the weakening of traditional alignments, these major changes have had significant impact on different aspects of the Belgian political system, such as voter’s volatility or coalition building. The political crises of 2007 and 2010–2011 around the formation of the federal cabinet exemplify this new era of political instability in Belgium.