  The VLT-FLAMES Survey of Massive Stars was an ESO Large Programme to
understand rotational mixing and stellar mass-loss in different metallicity
environments, in order to better constrain massive star evolution. We gathered
high-quality spectra of over 800 stars in the Galaxy and in the Magellanic
Clouds. A sample of this size is unprecedented, enabled by the first
high-resolution, wide-field, multi-object spectrograph on an 8-m telescope. We
developed spectral analysis techniques that, in combination with non-LTE,
line-blanketed model atmospheres, were used to quantitatively characterise
every star. The large sample, combined with the theoretical developments, has
produced exciting new insights into the evolution of the most massive stars.
