Single-crystal neutron-diffraction data were obtained for metallic erbium at sample temperatures from 4.2 to 298°K. Three distinct regions of long-range magnetic order were observed. In the high-temperature region (52-80°K) the ordered moments are confined to the c-axis direction and are sinusoidally modulated with a modulation wavelength of 3.5C0. The amplitude of this modulation saturates at 52°K with μz()=7.6 μBEr3+. Below 52°K the basal-plane component of the moment begins to order, and a third-order modulation along the c axis is observed. These effects are interpreted on the basis of a squared elliptical spiral with its major axis tilted relative to the crystal c axis. However, the structural details in this region are obscured by a temperature variation of the modulation wavelength and by the incommensurability of the modulation and the lattice. In the low-temperature region (4.2-20°K) a ferromagnetic spiral structure is indicated. At saturation the ferromagnetic c-axis component is 7.9 μBEr3+ and the spiral basal-plane component is 4.3μB/Er3+. The total ordered moment is then the free-ion value of 9.0μB/Er3+.