A lightweight, compact electric drive unit provides high reduction ratios for a bicycle, light electric vehicle or autonomous device. A cycloid gear reducer includes one or more cycloid gears within a housing. The cycloid gears interact with gear teeth on the inside surface of the housing, and ride on a cam shaft having eccentric lobes. Output pins extend through apertures in the cycloid gears, from an input carrier to an output carrier. An electric motor powers the cam shaft, while the output carrier powers a drive train.