Palm Valley is a census-designated place (CDP) in St. Johns County, Florida, United States. The population was 19,860 at the 2000 census.

Long past the first Spanish settlers arrived, there was an Indian village in what is known as Palm Valley today. Several Indian mounds have been outdoor revealing points, pottery and human skeletons. Early Franciscan missionaries constructed a mission in the area called The Nativity of Our Lady of Tolomato.

By 1703, Don Diego Espinoza had contracted in what is today the Palm Valley area. His immense ranch and the surrounding territory was known as Diego Plains. In the 1730s, the ranch was fortified to protect its inhabitants from Indian attack. By 1739, Great Britain and Spain were at raid and upset was brewing for the Diego Plains settlers. British general James Oglethorpe was commissioned to harass the Spanish settlements south of the colony of Georgia, so the Spanish executive fortified the Diego farmhouse which was already bodily called Fort San Diego. After Oglethorpe’s failure to take over St. Augustine, the Spanish military forlorn Fort San Diego, but further inhabitants moved into the area, living off the estate and the cattle.

In 1908, a canal was dug through Diego Plains connecting the San Pablo River to the north afterward the Tolomato River near St. Augustine to the south. This intracoastal canal made right of entry to the valley much easier for the residents that had settled in this area. In supplement to raising cattle, they farmed, logged, and sold palm fronds to religious groups. The many palm trees growing in the region led some of the settlers to decide upon the publicize Palm Valley for their community.