Type IV pili (T4P) are dynamic surface fibers that mediate diverse bacterial activities, including adhesion, twitching motility, horizontal gene transfer, biofilm formation, and virulence. The PilY family of T4P-associated proteins are found across a wide range of bacterial species and are critical for key T4P functions. PilY proteins are characterized by a shared domain architecture which consists of a variable N-terminal region that mediates adhesion and a conserved C-terminal beta-propeller domain that facilitates pilus biogenesis. Given their surface exposure and roles in virulence, PilY family proteins represent an attractive target for novel therapeutic interventions, including small-molecule antivirulence therapies against pathogenic bacteria and potential as vaccine antigens. This review synthesizes our current understanding of PilY structure, localization, function, and evolutionary relationships across T4P systems.