Electronic nematicity, a unidirectional self-organized state that breaks the rotational symmetry of the underlying lattice(1,2), has been observed in the iron pnictide(3-7) and copper oxide(8-11) high-temperature superconductors. Whether nematicity plays an equally important role in these two systems is highly controversial. In iron pnictides, the nematicity has usually been associated with the tetragonal-to-orthorhombic structural transition at temperature T-s. Although recent experiments(3-7) have provided hints of nematicity, they were performed either in the low-temperature orthorhombic phase(3,5) or in the tetragonal phase under uniaxial strain(4,6,7), both of which break the 90 degrees rotational C-4 symmetry. Therefore, the question remains open whether the nematicity can exist above T-s without an external driving force. Here we report magnetic torque measurements of the isovalent-doping system BaFe2(As1-xPx)(2), showing that the nematicity develops well above T-s and, moreover, persists to the non-magnetic superconducting regime, resulting in a phase diagram similar to the pseudogap phase diagram of the copper oxides(8,12). By combining these results with synchrotron X-ray measurements, we identify two distinct temperatures-one at T*, signifying a true nematic transition, and the other at T-s (