Seleucia on the Euphrates: Hellenistic town in ancient Iraq.
The Seleucids Accessions Chronicle (BCHP 10) suggests that the city was "on the Euphrates and the Royal Canal". This make Sippar and Nehardea likely candidates, unless this is a scribal error, and in fact "Tigris and Royal Canal" is meant (and therefore, Seleucia on the Tigris).
The Astronomical Diary of 106/105 mentions the town as residence of a satrap. In that same year, according to the same source, the city's territory was attacked by Arabs. The Diary of 94/93 records that a new branch of the Royal Canal was being dug, "above Seleucia on the mountain side".
A discussion of all available sources can be found here.