  We report the discovery and validation of two long-period giant exoplanets
orbiting the early K dwarf TOI-4600 (V=12.6, T=11.9), first detected using
observations from the Transiting Exoplanet Survey Satellite (TESS) by the TESS
Single Transit Planet Candidate Working Group (TSTPC-WG). The inner planet,
TOI-4600 b, has a radius of 6.80$\pm$0.31 R$_{\oplus}$ and an orbital period of
82.69 d. The outer planet, TOI-4600 c, has a radius of 9.42$\pm$0.42
R$_{\oplus}$ and an orbital period of 482.82 d, making it the longest-period
confirmed or validated planet discovered by TESS to date. We combine TESS
photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and
191 K, respectively, TOI-4600 b and c add to the small but growing population
of temperate giant exoplanets that bridge the gap between hot/warm Jupiters and
the solar system's gas giants. TOI-4600 is a promising target for further
transit and precise RV observations to measure masses and orbits for the
planets as well as search for additional non-transiting planets. Additionally,
with Transit Spectroscopy Metric (TSM) values of $\sim$30, both planets are
amenable for atmospheric characterization with JWST. Altogether will lend
insight into the formation and evolution of planet systems with multiple giant
exoplanets.
