An explicit expression of the pure vector superfield is derived in gauge theories in the Wess-Zumino gauge. A pure vector superfield means that the theta independent part of the superfield transforms as a Lorentz vector. This is to be contrasted with the so-called general scalar superfield, whose theta independent part is a scalar, as well as with the known spinor superfield, whose theta independent part is a spinor, which both contain a vector field. In contrast to the latter two superfields, the action of supersymmetric gauge theories follows directly from the theory of a pure vector superfield from a so-called D-term. As the construction of a supersymmetric gauge theory of Yang-Mills vector Bosons, is more naturally generated out of a pure vector supersfield and not of a scalar or a spinor, the importance of a pure vector superfield cannot be overemphasized.