We report the discovery and characterization of a transiting warm sub-Neptune planet around the nearby bright ($V=8.75$ mag, $K=7.15$ mag) solar twin HD 183579, delivered by the Transiting Exoplanet Survey Satellite (TESS). The host star is located $56.8pm0.1$ pc away with a radius of $R_{ast}=0.97pm0.02 R_{odot}$ and a mass of $M_{ast}=1.03pm0.05 M_{odot}$. We confirm the planetary nature by combining space and ground-based photometry, spectroscopy, and imaging. We find that HD 183579b (TOI-1055b) has a radius of $R_{p}=3.53pm0.13 R_{oplus}$ on a $17.47$ day orbit with a mass of $M_{p}=11.2pm5.4 M_{oplus}$ ($3sigma$ mass upper limit of $27.4 M_{oplus}$). HD 183579b is the fifth brightest known sub-Neptune planet system in the sky, making it an excellent target for future studies of the interior structure and atmospheric properties. By performing a line-by-line differential analysis using the high resolution and signal-to-noise ratio HARPS spectra, we find that HD 183579 joins the typical solar twin sample, without a statistically significant refractory element depletion.
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