Recent years have witnessed a growing interest in case studies and surveys by researchers of second language acquisition (SLA) and cognitive (neuro-)science to probe into the group of exceptionally talented multilingual learners or polyglots who can understand and speak an impressive number of multiple foreign languages other than their own mother tongue. The current paper reviews these latest developments and elucidates the phenomenon of (hyper-)polyglottism by tracing and analyzing its definitions and synthesizing and highlighting the key findings of case studies and large-scale surveys. Specifically, we aim to illuminate the complex and intricate relationships between hyperpolyglots' exceptional multilingual talents and their individual differences in language aptitude and other cognitive abilities such as IQ, personality traits, motivational characteristics, and language genetic variations, as well as their brain mechanisms and neural networks. The present paper calls upon concerted efforts from multiple disciplines to determine the critical cognitive abilities and pivotal developmental stages underlying the exceptional performance of these multilingual talents and hyperpolyglots.