The GALAH+ survey: Third data release

The ensemble of chemical element abundance measurements for stars, along with precision distances and orbit properties, provides high-dimensional data to study the evolution Milky Way. With this third release Galactic Archaeology HERMES (GALAH) survey, we publish 678 423 spectra 588 571 mostly nearby stars (81.2% are within <2 kpc), observed spectrograph at Anglo-Australian Telescope. This (hereafter GALAH+ DR3) includes all observations from GALAH Phase 1 (bright, main, faint 70%), K2-HERMES (17%), TESS-HERMES (5%), a subset ancillary (8%) including bulge >75 stellar clusters. We derive parameters $T_\text{eff}$, $\log g$, [Fe/H], $v_\text{mic}$, $v_\text{broad}$ & $v_\text{rad}$ using our modified version spectrum synthesis code Spectroscopy Made Easy (SME) 1D MARCS model atmospheres. break spectroscopic degeneracies in analysis astrometry $Gaia$ DR2 photometry 2MASS. report ratios [X/Fe] 30 different elements (11 which based on non-LTE computations) covering five nucleosynthetic pathways. describe validations accuracy precision, flagging peculiar stars/measurements recommendations results. Our catalogue comprises 65% dwarfs, 34% giants, 1% other/unclassified stars. Based unflagged composition age, find 62% young low-$\alpha$, 9% high-$\alpha$, 27% old 2% $\mathrm{[Fe/H]} \leq -1$. kinematics, 4% halo Several Value-Added-Catalogues, ages dynamics, updated after eDR3, accompany allow chrono-chemodynamic analyses, as showcase.