  We derive a distance of $15.8\pm0.4$ Mpc to the archetypical Seyfert 1 galaxy
NGC 4151 based on the near-infrared Cepheid Period-Luminosity relation and new
Hubble Space Telescope multiband imaging. This distance determination, based on
measurements of 35 long-period ($P > 25$d) Cepheids, will support the absolute
calibration of the supermassive black hole mass in this system, as well as
studies of the dynamics of the feedback or feeding of its active galactic
nucleus.
