A new and distinct plum tree variety, Prunus salicina, cv. ‘；Suplumfiftyfive’； is characterized by having early-ripening fruit that is large, with black skin and red flesh. The fruit of the new variety ‘；Suplumfiftyfive’； also has firm flesh, a sweet-mild flavor and a stone that is semi-free from the flesh. The date of ripening of the fruit of the new variety is approximately June 10.
