Quercus affinis is a species of oak native only to Mexico, mostly to the Sierra Madre Oriental pine-oak forests.

Trees produce flowers and catkins in the spring, which by autumn mature into small, rounded acorns up to 1.5 cm long.

Its range includes the Sierra Madre Oriental of Nuevo León, Tamaulipas, San Luis Potosí, Guanajuato, Querétaro, Hidalgo, and Veracruz states, the eastern Trans-Mexican Volcanic Belt of Veracruz and Puebla, and the Sierra Madre de Oaxaca of Puebla and Oaxaca, with some outlying populations in the Sierra Madre del Sur of Guerrero.

[1] Quercus affinis is typically found in cloud forest, frequently associated with Liquidambar styraciflua.

Other threats include habitat loss from forest clearing for cattle pasture and agriculture.