The cognitive, neural, and linguistic mechanisms underlying the comprehension and production of language are complex. This complexity is compounded when we consider the fact that the majority of people in the world learn, master, and switch between multiple languages. One way that we can track the complex dynamics of language use in the brain is through the direct recording of brain electrical activity. In this chapter, we review studies of human event-related brain potentials (ERPs) and their use in elucidating the mechanisms of language processing and multilingualism. First, we introduce ERPs, discussing the neural origins of the signal, methods for ERP recording, and the many benefits of ERP measures for language research. We then discuss major ERP components, stable and reliable features of the ERP signal that reflect different aspects of sensory, perceptual, and higher-order cognitive functioning, with a focus on application to language processing in both monolingual and multilingual language contexts.