Catalytic systems that are readily modifiable to achieve olefin migration or remote functionalization are highly sought-after in chemical synthesis. Here, we show that the combination of a commercially available nickel(II) pre-catalyst and a secondary phosphine oxide ligand enables site- and stereoselective alkene transposition for up to nine double-bond migrations within terminal and internal olefins under mild reductive conditions. Substrates bearing diverse functionalities including Brønsted acidic and reducible carbonyl groups are tolerated. Mechanistic and spectroscopic studies revealed the in situ generation of a catalytically active nickel-hydride species triggered by oxidative addition of the phosphine oxide. The reaction is amenable to regioconvergent isomerization as well as β-selective remote hydrophosphination when stoichiometric secondary phosphine oxide/base were employed.