North Tustin is a census-designated place and unincorporated community in Orange County, California. The population was 24,917 at the 2010 census, up from 24,044 at the 2000 census. It is Orange County's largest census-designated place. It is outside the city limits of Tustin and has 92705 and 92780 ZIP Codes. The CDP name was changed from Tustin Foothills in 2005. North Tustin is the largest unincorporated community in Orange County.