We report the results of a combined study of the normal-state resistivity and superconducting transition temperature Tc of the unconventional superconductor Sr2RuO4 under uniaxial pressure. There is strong evidence that, as well as driving Tc through a maximum at ∼3.5 K, compressive strains of nearly 1% along the crystallographic [100] axis drive the γ Fermi surface sheet through a van Hove singularity, changing the temperature dependence of the resistivity from T2 above, and below the transition region to T1.5 within it. This occurs in extremely pure single-crystals in which the impurity contribution to the resistivity is &lt
100 nΩ cm, so our study also highlights the potential of uniaxial pressure as a more general probe of this class of physics in clean systems.