Abstract The managed exploitation of thermal and mineral waters began at British spas in the middle of the 16th century when the first scientific treatises were written. The peak in popularity was reached in the 18th century, after which usage declined. Britain’s spa heritage is well preserved at some sites and 14 of these are selected for detailed discussion. These heritage spas are divided into three groups on the basis of their hydrogeology. In the first group, spa locations are both controlled and constrained by the hydrogeological conditions. Flows are reliable and the waters are generally highly mineralized as a result of long groundwater flow paths and residence times. In the second group, hydrogeology is of secondary importance and locations owe more to chance and the endeavours of local entrepreneurs. The waters are vulnerable to contamination and flows are often unreliable. The third group exists only because of human disturbance to natural groundwater flow paths. Of the hundreds of mineral springs in Britain, many of which were promoted as spas, most fell into the second group and have disappeared; these are remembered only by a street sign or a trickle of water.