Denmark Strait overflow water (DSOW) is one of the main components of the thermohaline circulation. There has been no consensus on where it is formed and by which way it is brought to the Denmark Strait. It is shown here that it is brought to the sill by a hitherto unknown current that is traced from the sill back into the Iceland Sea north of Iceland. The transport of this current is sufficient to account for a major part of the transport of DSOW as it has been measured at the sill if some entrainment of ambient water is assumed. This supports theories suggesting that the Iceland Sea is the main source for the DSOW and this has consequences for the way in which climate change affects the thermohaline circulation.