The Genesis mission sampled solar wind ions to document the elemental and isotopic compositions of the Sun and, by inference, of the protosolar nebula. Nitrogen was a key target element because the extent and origin of its isotopic variations in solar system materials remain unknown. Isotopic analysis of a Genesis Solar Wind Concentrator target material shows that implanted solar wind nitrogen has a N-15/N-14 ratio of 2.18 +/- 0.02 x 10(-3) (that is, approximate to 40% poorer in N-15 relative to terrestrial atmosphere). The N-15/N-14 ratio of the protosolar nebula was 2.27 +/- 0.03 x 10(-3), which is the lowest N-15/N-14 ratio known for solar system objects. This result demonstrates the extreme nitrogen isotopic heterogeneity of the nascent solar system and accounts for the N-15-depleted components observed in solar system reservoirs.