Lake Worth Beach, previously named Lake Worth, is a city in east-central Palm Beach County, Florida, United States, located about 63 miles (101 km) north of Miami. The city's name is derived from the body of water along its eastern border known as the Lake Worth Lagoon, which was named for General William J. Worth, who led United States Army forces during the last part of the Second Seminole War. Lake Worth Beach is situated south of West Palm Beach, southeast of Lake Clarke Shores, east of Palm Springs, and north of Lantana, while a small section of the city also partitions the town of Palm Beach. The 2010 census recorded a population of 34,910, which increased to 42,219 in the 2020 census. Lake Worth Beach is within the Miami metropolitan area, which was home to an estimated 6,138,333 people in 2020.

While archaeological evidence indicates that the Jaega inhabited nearby areas thousands of years ago, Samuel and Fannie James, an African American couple, became the first known settlers in modern-day Lake Worth Beach in 1885, filing a homestead claim on 187 acres (76 ha). Fannie James operated the Jewell Post Office from 1889 to 1903 to serve the few residents who lived between Lantana and West Palm Beach. A land development scheme by Bryant & Greenwood in the 1910s allowed buyers to receive a parcel of land if they purchased a lot in present-day Greenacres. Consequently, the population increased from 38 in July 1912 to 308 only five months later. The town of Lake Worth was incorporated in June 1913. Thereafter, Lake Worth grew rapidly during the 1920s land boom and in the decades following World War II. Residents voted to change the official name to Lake Worth Beach in 2019.

Today, Lake Worth Beach is a city featuring several historic neighborhoods, such as the National Register of Historic Places-listed College Park and Old Lucerne, while the downtown area also has dozens of buildings that are part of the Historic Old Town Commercial District. Lake Worth Beach is one of the most ethnically and racially diverse municipalities in Palm Beach County. Several cultural events are hosted annually in the city, including a street painting festival, several ethnic festivals, and Palm Beach Pride, one of the largest LGBTQIA+ pride festivals in Florida.