In Greek mythology, Erythrus (gr. Erythros) was

a son of Leucon, and grandson of Athamas. He was one of the suitors of Hippodameia, and the town of Erythrae, in Boeotia, was believed to have derived its name from him. (Pausanias vi. 21. 71; Müller, Orchom. p. 210. 2nd edit.)

a son of Rhadamanthus, who led the Erythraeans from Crete to the Ionian Erythrae. (Paus. vii. 3. § 4.) There are two other mythical personages of the name of Erythrus, or Erythrius, from whom the Boeotian Erythrae, and the Erythraean Sea, are said to have received their names respectively. (Eustath. ad Hom. p. 267; Steph. Byz. s. v. Eruthra; Curtius, viii. 9.)