Casalarreina is a town in the province of La Rioja, Spain. It lies in the north-western part of the province, about 47 kilometres (29 miles) from Logroño, the regional capital.
The town is one of the municipalities that make up the autonomous community of La Rioja, a region in northern Spain known for its wine production. Casalarreina sits within this wine-growing area, in the Ebro river valley that defines much of the province's geography and settlement pattern.
As a small Riojan municipality, it forms part of the local administrative structure of the province, with its own town council. Its position near Logroño places it within reach of the regional capital and the wider services and transport links centred there.