Rayleigh is a market town and civil parish in the District of Rochford in Essex, England, located between Chelmsford and Southend-on-Sea. It lies to the east of central London. It had a population of 30,196 in 2001, having expanded rapidly in the 1960s.
Rayleigh Urban District was an urban district in the county of Essex, England. It was created in 1929 by the merger of the civil parishes of Rayleigh and Rawreth, both previously in the Rochford Rural District.
Since April 1, 1974 it has formed part of the District of Rochford.