Low-dimensional materials with definite geometrical and electronic structures have long been pursued to fulfill the requirement of technological devices toward miniaturization, multifunctionality, and precise manufacturing. Inspired by the emerging transition metal halide monolayers with intriguing magnetic behavior, here we systematically explore stable one-dimensional (1D) structures of transition metal halides. By first-principles calculations, a total of 208 TMX2 and TMX3 (TM is 3d, 4d, 5d transition metal elements; X = F, Cl, Br, I) nanowires have been predicted, showing diverse electronic and magnetic properties, such as ferromagnetic semiconductors, half metals, and antiferromagnets. They possess many application-desired characters, including a wide range of bandgaps, small carrier effective masses, outstanding capability for solar energy harvesting, and strong ferromagnetic or antiferromagnetic order. This large family of TMXn nanowires provides a great platform for exploring exotic 1D physics as well as for designing high-performance devices.