Cortex may refer to:

• Cortex (anatomy), the outermost or superficial layer of an organ
• Cortex (archaeology), the outer layer of rock formed on the exterior of raw materials by chemical and mechanical weathering processes
• Cortex (botany), the outer portion of the stem or root of a plant
• Cortex (hair), the middle layer of a strand of hair

The Cortex Plus System is a toolkit RPG system that evolved from Margaret Weis Productions, Ltd's Cortex System. It has been used for three published games and one published preview to date, and the design principles are in the Cortex Plus Hackers Guide, a book of advice in how to create new games using Cortex Plus, and list of new games produced via kickstarter. According to the Hackers' Guide there are three basic 'flavours' of Cortex Plus; Action, Drama, and Heroic.