We investigate the relation between circular velocity vc and bulge velocity dispersion σ in spiral galaxies, based on literature data and new spectroscopic observations. We find a strong, nearly linear vc−σ correlation with a negligible intrinsic scatter, and a striking agreement with the corresponding relation for elliptical galaxies. The least massive galaxies (σ<80 km s−1) significantly deviate from this relation. We combine this vc−σ correlation with the well-known MBHσ relation to obtain a tight correlation between circular velocity and supermassive black hole mass, and interpret this as observational evidence for a close link between supermassive black holes and the dark matter haloes in which they presumably formed. Apart from being an important ingredient for theoretical models of galaxy formation and evolution, the relation between MBH and circular velocity has the potential to become an important practical tool in estimating supermassive black hole masses in spiral galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html