The Pisuerga is a river in northern Spain, the Duero's second largest tributary.

It rises in the Cantabrian Mountains in the province of Palencia, autonomous region of Castile and León.

Since the 1950s the water level of the river has been very regular throughout the year due to the huge Aguilar de Campoo dam which collects all the water from the river's rainy upper valleys.

This regulation has allowed the creation of vast extensions of irrigated farmland along the Pisuerga's course across the northern Castilian plain.

The Spanish phrase aprovechando que el Pisuerga pasa por Valladolid ("And now since Pisuerga crosses Valladolid") is a popular way to point out or acknowledge a non sequitur since the river has no bearing with the following "consequence".