Seybouse (in Algerian Arabic: وادي سيبوس, romanized: Oued Seybouse) is a river in northeastern Algeria, near the border with Tunisia. In Roman times, it was called the Ubus.

The river runs for about 225 kilometres (140 mi), flowing through Guelma and Annaba Provinces. It starts in Medjez Amar, in the Tell Atlas north-west of Guelma Province. Its flows into the Mediterranean Sea at Seybouse (called Joannonville under French rule) to the south-east of the city of Annaba. Its mouth is just north of Sidi Salem, the site of Hippo Regius where Saint Augustine lived in AD 391–430.

The Seybouse is used for irrigation of agricultural areas, but it is becoming polluted because of industrial activities.

(As of 1998; source: ANRH)

Element	Amount
Flow	11.5 m/s
Temperature	21.41 °C
pH	8.21
Oxygen saturation	36.61%
DBO	18.33
DCO	124.3
Nitrates (NO3)	5.58
PO4	2.29
Ammonium	9.18

• (in French) ANRH (National Agency for Water Resources)
• Augustine in Algeria
• 1902 Encyclopedia