"Seaside Island" may refer to:
Levels[]
- Seaside Island (level), the level in Sonic Boom: Fire & Ice.
Locations[]
- Seaside Island, the main setting in the Sonic Boom franchise.
- Seaside Island (Mirror Dimension), the location in the Mirror Dimension
- Seaside Island (alternate dimension), the location in the alternate reality of the Sonic Boom World.