Materials hosting kagome lattices have drawn interest for the diverse magnetic and electronic states generated by geometric frustration. In the AV3Sb5 compounds (A=K, Rb, Cs), stacked vanadium kagome layers give rise to unusual charge density waves (CDW) and superconductivity. Here we report single-crystal growth and characterization of ScV6Sn6, a hexagonal HfFe6Ge6-type compound that shares this structural motif. We identify a first-order phase transition at 92 K. Single crystal x-ray and neutron diffraction reveal a charge density wave modulation of the atomic lattice below this temperature. This is a distinctly different structural mode than that observed in the AV3Sb5 compounds, but both modes have been anticipated in kagome metals. The diverse HfFe6Ge6 family offers more opportunities to tune ScV6Sn6 and explore density wave order in kagome lattice materials.