The Walker circulation is an atmospheric circulation of air at the equatorial Pacific Ocean, responsible for creating ocean upwelling off the coasts of Peru and Ecuador. This brings nutrient-rich cold water to the surface, increasing fishing stocks. It was discovered by the English physicist Sir Gilbert Walker.

The Walker circulation is caused by the pressure gradient force that results from a high pressure system over the eastern pacific ocean, and a low pressure system over Indonesia. When the Walker circulation weakens or reverses, an El Nino results, causing the ocean surface to be warmer than average, as upwelling of cold water occurs less or not at all. An especially strong Walker circulation causes a La Nina, resulting in cooler ocean temperatures due to increased upwelling.