Klein is an unincorporated community in Harris County, Texas, United States, roughly bordering SH 99 to the north, SH 249 to the west, I-45 to the east, and the city of Houston to the south. It includes the entire area of Klein ISD. Residents of the zip codes 77066, 77069, 77086, 77379, 77388, 77389, and 77391 can use Klein as their postal city. Klein is one of the largest and most diverse unincorporated areas of Houston.