Examples of misinformation having real-world consequences aren’t hard to find, and misinformation has been a hugely important topic of discussion in popular media, among politicians, and in scientific research. This chapter discusses whether misinformation poses a problem for society: for example, by damaging the democratic process or fostering potentially problematic health behaviors. We discuss competing perspectives in detail: scientists disagree over the extent to which misinformation can be harmful at a societal level, and what definition of “misinformation” is used matters a lot in determining the scope of the problem. The chapter concludes with a case study: information warfare in the present-day Russian–Ukrainian war.