Aliso Viejo is a city in Orange County, California. It has a population of 40,166 as of the 2000 census and an estimated population as of 2007 of 41,424. It became Orange County's 34th city on July 1, 2001, the only city in the county to incorporate since 2000. It is bordered by the cities of Laguna Beach on the west and southwest, Laguna Hills on the east, Laguna Niguel on the southeast, and Laguna Woods on the north.