(It. Anton. p. 170; Serapiu, Tab. Peut.), a large village seated near the junction of the canal of the Ptolemies with the Bitter Lakes, east of the Delta. Serapium was 18 miles distant from Heroopolis and 50 from Clysma, at the top of the Sinus Heroopolites. Its temple of Serapis, and its position on the canal that connected the Nile with the Red Sea, rendered it a place of considerable traffic.
It was probably founded, or at least enlarged, by the Ptolemies after Philadelphus (B.C. 274) had extended the canal to the Bitter Jakes.