This chapter discusses the proliferation of online echo chambers and its implications on the polarization of opinion in the digital environment. This phenomenon must be understood in the broader context of the fake news and digital disinformation. The chapter starts by providing some conceptual clarifications, arguing against using the rather limitative term of “fake news” to describe what is actually “disinformation 2.0”. Next, we discuss the features of online echo chambers, and the digital divide they create. Lastly, we discuss the impact of echo chambers in changing the patterns of news consumption, in lowering trust in news and the traditional media, and in facilitating online disinformation.