Follicular helper T (T_FH) cells are a class of helper T cells specialized in the cognate control of antigen-specific B cell immunity. Upon first contact with antigen-primed B cells, pregerminal center effector T_FH cells promote B cell clonal expansion, antibody isotype switch, plasma cell differentiation, and the induction of germinal centers. By contrast, within germinal centers, T_FH cells regulate the fate of antigen-specific GC B cells expressing high-affinity variant B cell receptors to promote memory B cell and long-lived plasma cell development. Recent studies unravel multiple signals controlling T_FH development and functional subtypes of antigen-specific T_FH cells, including memory T_FH cells that accelerate memory B cell responses to antigen rechallenge in vivo.