  We show that ulta-dense Z-pinches with nanoscale dimensions can be generated
by irradiating aligned nanowires with femtosecond laser pulses of relativistic
intensity. Using fully three-dimensional relativistic particle-in-cell
simulations we demonstrate that the laser pulse drives a forward electron
current in the area around the wires. This forward current induces return
current densities of $\sim$ 0.1 Giga-Amperes per $\mu$m\textsuperscript{2}
through the wires. The resulting strong, quasi-static, self-generated azimuthal
magnetic field pinches the nanowires into hot plasmas with a peak electron
density of $> 9\cdot 10^{24}$ cm\textsuperscript{-3}, exceeding 1000 times the
critical density. Arrays of these new ultra-dense nanopinches can be expected
to lead to efficient micro-fusion and other applications.
