Sebastian is a city in Indian River County, Florida, United States at the confluence of the St. Sebastian River and the Indian River. It is two miles away from the Atlantic Ocean. It is the largest city in Indian River County and the biggest population center between Palm Bay and Fort Pierce. The city's economy is heavily reliant on tourism. It has numerous resorts in the local area, such as Disney's Vero Beach Resort. It is very close to many natural and scenic areas like the Pelican Island National Wildlife Refuge, Sebastian Inlet State Park, and St. Sebastian River Preserve State Park.

Indian River County is a county located in the southeastern and east-central portions of the U.S. state of Florida. As of the 2020 census, the population was 159,788. Its seat is Vero Beach. It is Florida's 7th richest county and in 2000 was the 87th richest county in the U.S. by per capita income.