| Rai Coast (Rai Kos) District | |
| Other Name: | South Coast |
| Pushpin Map: | Papua New Guinea |
| Coordinates: | -5.501°N 145.85°W |
| Pushpin Label Position: | right |
| Pushpin Map Caption: | Location within Papua New Guinea |
| Subdivision Type: | Country |
| Subdivision Name: | Papua New Guinea |
| Subdivision Type1: | Province |
| Subdivision Name1: | Madang Province |
| Seat Type: | Capital |
| Seat: | Saidor |
| Area Total Km2: | 5433 |
| Population Total: | 83213 |
| Population As Of: | 2011 census |
| Population Density Km2: | auto |
| Demographics1 Title1: | Main languages |
| Timezone1: | AEST |
| Utc Offset1: | +10 |
Rai Coast District is a district in the southeast of Madang Province in Papua New Guinea. It is one of the six districts that of the Madang Province. The District has four local level government (LLG) areas namely; Astrolabe Bay, Nahu Rawa, (Nankina, Yupna & Domung (NAYUDO) and Saidor (formerly Rai Kos). The District has 84 ward areas. The largest local government area is Saidor which has 42 wards.
The District's headquarter or administrative center is located at Saidor in the Saidor LLG area. Historically, Saidor was the base for the allied forces during World War II, while the Astrolabe Bay LLG area was known by the Ukrainian anthropologist and explorer Miklouho-Maclay who landed in the area in September 1871 on his boat - Vitiaz. Today a memorial stands at Garagasi in Bongu village.
Geographically, Rai Coast District is the most difficult districts in Madang Province with mountains (Mt. Abirara & Mt. Aniabo) rising to more than 2,000 meters asl. Road accessibility is very limited to a track. Only during dry season, four wheel drive vehicles can be used. From Madang to the border, there are many fast running creeks and rivers and makes crossing difficult during wet season.
Many Rai Coast languages are spoken in this district.