Provided are a fully-shielded high-frequency connector and a connector assembly. The fully-shielded high-frequency connector includes an insulating base, a shell, a signal terminal and a shielding conductive stiffener. The insulating base includes an insulating body, a fitting portion and a gland portion, a first through hole structure and a second through hole structure. The signal terminal includes a contact portion, a connection portion and a mounting portion. The shielding conductive stiffener includes a tube structure, a fixing connection structure and a cover plate structure. The shell includes a main body portion, a bonding portion, a fixing portion and a snap portion. The fixing portion is electrically connected to the cover plate structure and an outer conductor of the coaxial cable. The bonding portion and the snap portion cooperate to assemble and fix the insulating base and the shell.