Abstract: A helmet comprising a shell and a chin guard. The chin guard has a first lateral portion, a second lateral portion and a front portion positioned between the first and second lateral portions, said chin guard being hingedly mounted to the shell and moveable between an open position and a closed position. The chin guard has a locking mechanism for locking the chin guard to the shell in the closed position. The locking mechanism comprises a first locking member applied at the first lateral portion and provided for engaging the shell in a locking position; a second locking member applied at the second lateral portion and provided for engaging the shell in the locking position; and an actuating member connected to said first and second locking members and provided for actuating the first and second locking members. The front portion has a first cavity and a second cavity faced towards each other.