An enzyme complex composed of two proteins, dinitrogenase and nitrogenase reductase; dinitrogenase is tetrameric with an alpha2-beta2 structure and nitrogenase reductase is a homodimer, and both are associated with metal ions, which differ between species. Both proteins are required for the enzyme activity of the complex, the formation of oxidized ferredoxin and ammonia from reduced ferredoxin and nitrogen.