| Klasop | |
| Name Other: | Klasof |
| Map: | Klasop and Klasagun estuary map.svg |
| Map Size: | 360px |
| Subdivision Type1: | Country |
| Subdivision Name1: | Indonesia |
| Subdivision Type2: | Province |
| Subdivision Name2: | Southwest Papua |
| Subdivision Type3: | Regency |
| Subdivision Name3: | Sorong |
| Mouth: | Segun Bay |
| Mouth Coordinates: | -1.4171°N 131.3191°W |
The Klasop or Klasof is a river in the northwest of the Bird's Head Peninsula of New Guinea. Its course generally runs in a southerly direction, and it flows into the bay of Segun, in a large estuary that is connected to that of the Klasagun River to the west. The large island of Jemur separates the two estuaries. The stream of Klawaralim is a left tributary in the upper reach, while in the lower reaches Klasop is joined by a number of right-hand tributaries, including Klamer and Klasafet. For much of its length, Klasop is surrounded by mangrove forests.