The present invention is a portable rowing machine that allows a user to perform rowing, skiing, paddling, or any other physical activities at any suitable location. The portable rowing machine contains a housing, a pulley, a flywheel, a planetary gear assembly, an anchor, a retraction mechanism, and a pull cord. The housing contains a central gear support. The pulley, the flywheel, the planetary gear assembly, and the retraction mechanism are positioned within the housing. The central gear support is positioned within the housing. The planetary gear assembly is positioned within the central gear support. The pulley and the flywheel are axially connected opposite to each other along the planetary gear assembly. The retraction mechanism is operatively connected to the pulley, where the retraction mechanism is configured to retract the pull cord into a spooled state around the pulley. The anchor is externally connected to the housing.