Nickel catalysis, within catalytic cross-coupling chemistry, is the use of nickel complexes to mediate carbon–carbon and carbon–heteroatom bond construction through organonickel intermediates that cycle among accessible oxidation states, commonly Ni(0)/Ni(II) and Ni(I)/Ni(III) ^[1]. The concept is bounded by elementary steps of oxidative addition, transmetalation or radical capture, and reductive elimination at a nickel center, and it excludes processes in which nickel functions only as a stoichiometric reductant. Essential features include the earth-abundant metal’s comparatively high electropositivity, its ready access to one-electron pathways, and its capacity to activate bonds that are reluctant toward palladium, including certain C–O, C–N, and C–Cl linkages ^[1][2]. Dual catalytic manifolds merge a photoredox cycle with a nickel cycle so that an alkyl radical is captured by nickel and then coupled with an aryl electrophile ^[2][3]. Nickel also promotes the Nozaki–Hiyama–Kishi addition of alkenylchromium reagents generated from alkenyl triflates ^[4]. The field is distinguished from palladium catalysis by the greater incidence of radical elementary steps and by a different functional-group activation profile.