Well-resolved far-ultraviolet spectroscopic images of O I, S I, and previously undetected H I Lyman-alpha emission from lo were obtained with the Hubble space telescope imaging spectrograph (STIS), Detected O I and S I lines (1250 to 1500 angstroms) have bright equatorial spots (up to 2.5 kilorayleighs) that shift position with jovian magnetic field orientation; limb glow that is brighter on the hemisphere facing the jovian magnetic equator; and faint diffuse emission extending to similar to 20 lo radii. All O I and S I features brightened by similar to 50 percent in the last two images, concurrently with a ground-based observation of increased iogenic [O I] 6300-angstrom emission. The H I Lyman-alpha emission, consisting of a small, similar to 2-kilorayleigh patch near each pole, has a different morphology and time variation.