Abstract: A baseball or softball swing training device facilitates one-armed batting practice by allowing the selected batter's arm, and the bat held thereby, to swing through a strike zone, while the batter's opposite arm and hand remain substantially stationary. A wheeled, lower base assembly comprising a horizontal base plate resting on a flat supporting surface supports an upright, vertical stanchion that telescopically and adjustably receives a rigid, adjustable elbow. The elbow has a vertical portion slidably coupled to the stanchion, and an integral outwardly projecting, normally horizontal portion that slidably and telescopically receives an accessory mounting tube. A user-grasped handle assembly supported by the mounting tube terminates in a vertically oriented handle grasped by the batter during a swing. The stanchion and mounting tube and base plate border and define a strike zone through which the batter's free hand and bat travel during a practice swing.