This paper serves as the introduction for a special issue investigating the current status of the new EU mobility regime (Favell, 2008b) close to 20 years after the first eastward enlargement. Our main claim is that EU labour mobility is shaped by and has created multiple hierarchies across the EU and within EU countries, as is evident in the unequal labour market outcomes of different groups of mobile EU workers. The EU migration regime has grown more complex and diversified over the years, but underneath this complexity remain strong hierarchies that structure the patterns and consequences of mobility. We therefore propose the concept of “hierarchized mobility” to grasp the complex yet unequal mobility opportunities of workers within the EU. Moreover, we argue that to understand this hierarchized mobility, both socio-economic factors and regulation should be studied. On the one hand, enduring hierarchies between national labour markets shape EU labour mobility and transform these hierarchies into hierarchies within national labour markets (Felbo-Kolding et al., 2019). On the other hand, both national and EU policies regulate and shape mobility and the hierarchies it creates (Scholten and van Ostaijen, 2018). The interaction between EU rules that shape different categories of mobile workers and national social and labour market regulation can counteract or reinforce the trend towards hierarchized mobility.