Cardiff-by-the-Sea, usually referred to as Cardiff, is a beach community in the incorporated city of Encinitas in San Diego County, California.

The Pacific Ocean is to the west of Cardiff-by-the-Sea, the rest of incorporated Encinitas is to the east and north, and a beach and lagoon to the south.

[2] Frank Cullen's wife, Esther, a native of Cardiff, Wales, persuaded him to name the community "Cardiff-by-the Sea", as well as naming many streets after other cities in Britain, such as the English "Birmingham", "Oxford", "Chesterfield" and "Manchester", despite heavy Spanish influence in the area.

Cardiff became a destination for people seeking a tight-knit community to raise children, start a business and live in close proximity to the ocean.

When the tide is low, a flat rock reef is revealed that extends 50 yards from shore.