How important are firms for wage inequality in developing countries where structural unemployment is high? Research focused on contexts close to full employment has suggested a substantial role of firms in labor market inequality. Using matched employer–employee data from South Africa, I find that firms explain a larger share of wage variation than in richer countries. I consider drivers of this, documenting first a higher productivity dispersion as found for other developing countries. Secondly, I estimate the separations elasticity by instrumenting wages of matched workers with firm wages, and I find a low separations elasticity. This generates a high degree of monopsony, and the correspondingly high estimated rent-sharing elasticity helps explain the important role of firm wage policies in inequality. Monopsony may be driven by higher unemployment, and regional heterogeneity provides suggestive evidence for this. Such firm-level competitive dynamics may exacerbate inequality in developing countries more generally.