A single-electron memory, in which a bit of information is stored by one electron, is demonstrated at room temperature, The memory is a floating gate metal-oxide-semiconductor transistor in silicon with a channel width (similar to 10 nanometers) smaller than the Debye screening length of a single electron and a nanoscale polysilicon dot (similar to 7 nanometers by 7 nanometers) as the floating gate embedded between the channel and the control gate, Storing one electron on the floating gate screens the entire channel from the potential on the control gate and leads to (i) a discrete shift in the threshold voltage, (ii) a staircase relation between the charging voltage and the shift, and (iii) a self-limiting charging process. The structure and fabrication of the memory should be compatible with future ultralarge-scale integrated circuits.