  We propose gauge theories in which the unstable branes and the fundamental
string are realized as classical solutions. While the former are represented by
domain wall like configurations of a scalar field coupled to the gauge field,
the latter is by a confined flux tube in the bulk. It is shown that the
confined flux tube is really a source of the bulk B-field. Our model also
provides a natural scenario of the confinement on the brane in the context of
the open string tachyon condensation. It is also argued that the fundamental
string can be realized as a classical solution in a certain IIB matrix model as
in our model.
