  We present the new TNG50 cosmological, magnetohydrodynamical simulation --
the third and final volume of the IllustrisTNG project. This simulation
occupies a unique combination of large volume and high resolution, with a 50
Mpc box sampled by 2160^3 gas cells (baryon mass of 8x10^4 Msun). The median
spatial resolution of star-forming ISM gas is ~100-140 parsecs. This resolution
approaches or exceeds that of modern 'zoom' simulations of individual massive
galaxies, while the volume contains ~20,000 resolved galaxies with M*>10^7
Msun. Herein we show first results from TNG50, focusing on galactic outflows
driven by supernovae as well as supermassive black hole feedback. We find that
the outflow mass loading is a non-monotonic function of galaxy stellar mass,
turning over and rising rapidly above 10^10.5 Msun due to the action of the
central black hole. Outflow velocity increases with stellar mass, and at fixed
mass is faster at higher redshift. The TNG model can produce high velocity,
multi-phase outflows which include cool, dense components. These outflows reach
speeds in excess of 3000 km/s out to 20 kpc with an ejective, BH-driven origin.
Critically, we show how the relative simplicity of model inputs (and scalings)
at the injection scale produces complex behavior at galactic and halo scales.
For example, despite isotropic wind launching, outflows exhibit natural
collimation and an emergent bipolarity. Furthermore, galaxies above the
star-forming main sequence drive faster outflows, although this correlation
inverts at high mass with the onset of quenching, whereby low luminosity,
slowly accreting, massive black holes drive the strongest outflows.
