A connector includes a housing and a slide holder. The housing includes a lock portion maintaining a completely fitted state with a mating housing. The slide holder is configured to be mounted on the housing so as to be movable in a fitting direction of the housing and the mating housing between a temporary locking position and a main locking position, and is movable from the temporary locking position to the main locking position while avoiding interference with the lock portion only in the completely fitted state. The housing includes a pair of protective walls extending in the fitting direction so as to sandwich the lock portion and the slide holder in a width direction orthogonal to the fitting direction.