| Ci Ujung | |
| Name Other: | Ujung river, Ciujung river |
| Mouth Location: | Tengkurak, Tirtayasa, Serang, Banten |
| Subdivision Type1: | Country |
| Mouth Coordinates: | -5.9629°N 106.3569°W |
| Pushpin Map: | Indonesia Java |
| Pushpin Map Caption: | Location in Java |
| Basin Size: | 2159km2 |
| River System: | Ciujung basin |
| Source1: | Mount Halimun Salak National Park |
| Source2 Location: | Lebak Regency |
The Ciujung (Ujung River) is a river in the province of West Java and Banten on the island of Java, Indonesia.
The rivers in Banten, the westernmost province of Java, run roughly parallel to each other. The main ones are the Peteh, called the Banten on the lower reaches near the city of Kota Banten, the Ujung, which enters the sea at Pontang, the Durian, which enters the sea at Tanara, the Manceuri, and the Sadane, which rises in the mountainous region of Priyangan and 1682 formed the border between the Dutch East India Company (VOC) territory and Batavia (modern Jakarta). The rivers fan out into deltas near the coast. The Ciujung discharges into the of Banten Bay.
The original inhabitants of the mouths of Ci Ujung, Ci Durian, and Ci Banten rivers were Sundanese people. In 1682 there were paddy fields on the lower reaches of the Ujung and Durian. Pontang Port and the Ciujung River used to be important for carrying merchandise into the interior. The river itself sits on an elevation of 10 meters.