The relation between momentum and thermal transport in neutral‐beam‐heated tokamaks with subsonic toroidal rotation velocity has been investigated. A theory of diffusive momentum transport driven by ion‐temperature‐gradient‐driven turbulence (&eegr;iturbulence) is presented. In addition, the level of &eegr;iturbulence is enhanced by radially sheared toroidal rotation. The resulting ion shear viscosity is &khgr;&Jgr;=1.3{(1+&eegr;i)/&tgr;+[(Ln/2cs) (dV0/dr)]2}2(&rgr;2scs/Ls). The associated ion thermal diffusivity, &khgr;i, is identical to &khgr;&Jgr;. Thus a scenario based on velocity‐shear‐enhanced &eegr;iturbulence is consistent with the experimentally observed relationship between thermal and momentum confinement.