COSMOS Spectroscopic Redshift Compilation (First Data Release): 165k Redshifts Encompassing Two Decades of Spectroscopy

We present the COSMOS Spectroscopic Redshift Compilation encompassing ~ 20 years of spectroscopic redshifts within the 2 deg² COSMOS legacy field. This compilation contains 165,312 redshifts of 97,929 unique objects from 108 individual observing programs up to z ~ 8 with median stellar mass ~ 10⁹ to 10¹⁰ M_ (redshift dependent). Rest-frame $NUVrJ$ colors and SFR -- stellar mass correlations show the compilation primarily contains low- to intermediate-mass star-forming and massive, quiescent galaxies at $z < 1.25$ and mostly low-mass bursty star-forming galaxies at $z > 2$. Sources in the compilation cover a diverse range of environments, including protoclusters such as ``Hyperion''. The full compilation is 50% spectroscopically complete by i ~ 23.2 and Kₛ ~ 21.3 mag; however, this is redshift dependent. Spatially, the compilation is $>50$% complete within the CANDELS area, while the outer regions of COSMOS are $>10$% complete limited to $i < 24$ mag and KS < 22.5 mag, separately. We demonstrate how the compilation can be used to validate photometric redshifts and investigate calibration metrics. By training self-organizing maps on COSMOS2020/Classic and projecting the compilation onto it, we find key galaxy subpopulations that currently lack spectroscopic coverage including $z < 1$ intermediate-mass quiescent galaxies and low-/intermediate-mass bursty star-forming galaxies, z ~ 2 massive quiescent galaxies, and $z > 3$ massive star-forming galaxies. This approach highlights how combining self-organizing maps with our compilation can provide guidance for future spectroscopic observations to get a complete spectroscopic view of galaxy populations. Lastly, the compilation will undergo periodic data releases that incorporate new spectroscopic redshift measurements, providing a lasting legacy resource for the community.