A portable bulk transfer pump assembly (10) constructed in accordance with the principles of a preferred embodiment of the present invention is configured for transferring fluid (not shown) in bulk. The illustrated portable bulk transfer pump assembly (10) broadly includes a portable housing (12) that carries a pumping assembly (14). The portable housing (12) is sized and configured to both support the pumping assembly (14) and enable the entire pump assembly (10) to be readily and easily manually transported to and from pumping locations. The pumping assembly (14) is configured to pump low, medium, and high viscosity fluids utilizing a single pump (52) and a drive assembly (54) drivingly coupled to the pump (52) and selectively adjustable to operate the pump (52) at varying speeds. The illustrated drive assembly (54) includes a motor (80) and a variable speed transmission (82) disposed between the motor (80) and the pump (52).