We propose a simple closed-form expression relating [...] the mean relative velocity of pairs of galaxies at fixed separation r—to the two-point correlation function of mass density fluctuations,[...]. Our Ansatz is an interpolation between the perturbative and stable clustering expressions for [...]. We compare our analytic model for [...] with N-body simulations and find excellent agreement in the entire dynamical range probed by the simulations ([...]). Our results can be used to estimate the cosmological density parameter, Ω, directly from redshift-distance surveys.