Sanibel is a city in Lee County, Florida, United States. As of the 2000 census, the city had a total population of 6,064. As of 2004, the population recorded by the U.S. Census Bureau is 6,102. The city is on Sanibel Island on the Gulf coast of Southwest Florida, and is linked to the mainland by the Sanibel Causeway. A short bridge over Blind Pass links Sanibel to the unincorporated town of Captiva on Captiva Island.

According to the United States Census Bureau, the city has a total area of 85.9 km² (33.2 mi²). 44.6 km² (17.2 mi²) of it is land and 41.3 km² (16.0 mi²) of it (48.13%) is water. As of the census of 2000, there were 6,064 people, 3,049 households, and 2,125 families residing in the city. The population density was 136.0/km² (352.4/mi²). There were 7,075 housing units at an average density of 158.7/km² (411.2/mi²). The racial makeup of the city was 97.99% White, 0.94% African American, 0.08% Native American, 0.33% Asian, 0.05% Pacific Islander, 0.12% from other races, and 0.49% from two or more races. Hispanic or Latino of any race were 1.39% of the population.