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HR 8799 harbors arguably the first and best-studied directly-imaged planets.In this brief article, I describe how the HR 8799 planetary system is abenchmark system for studying the atmospheres, orbital properties, dynamicalstability, and formation of young superjovian planets. Multi-wavelengthphotometry and spectroscopy show that HR 8799 bcde appear to have thickerclouds than do field brown dwarfs of similar effective temperatures and exhibitevidence for non-equilibrium carbon chemistry, features that are likelyconnected to the planets' low surface gravities. Over 17 years of astrometricdata constrain the planets' orbits to not be face on but possibly in multipleorbital resonances. At orbital separations of 15--70 au and with masses of$\approx$ 5--7 $M_{\rm J}$, HR 8799 bcde probe the extremes of jovian planetformation by core accretion: medium-resolution spectroscopy may provide cluesabout these planets' formation conditions. Data from the next generation of 30m-class telescopes should better constrain the planets' orbits, chemistry,gravity, and formation history.

HR 8799: The Benchmark Directly-Imaged Planetary System