A dumbbell with a selectable number of weight disks includes a handle with projectable pins in opposing directions, with end surfaces, a base assembly for accommodating two sets of weight disks standing upright, the weight disks having central openings. The projection lengths of the pins are stepwise selectable by an indexing device in order thereby to permit selection of the number of weight disks supported on the handle. Neighboring weight disks and the handle have mutually engaging connecting arrangements which axially interconnect the weight disks and the handle but which permit radial separation. In order to prevent the set projection lengths of the pins from being unintentionally altered, when a dumbbell lifted up out of the base assembly is used, the handle has a locking arrangement which locks the pins in the set projection positions.