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A three‐region Campbell (TRC) type model for predicting undisturbed soil unsaturated hydraulic conductivity from water retention is presented. The model assumes that hydraulic conductivity follows separate Campbell functions within the macropore (matric head ψ > −10 cm H₂O), the mesopore (−10 ≥ ψ > −350 cm H₂O), and the micropore (ψ ≤ −350 cm H₂O) regions, and that soil water retention and two reference‐point values of hydraulic conductivity are known. Conductivity and retention data for 100 undisturbed soils from the UNSODA database and 68 soils from a Danish database were used for model development. Conductivity for both highly structured (three‐region) and weakly structured (two‐region) soils mostly followed a piecewise linear function (with slope β) in a Log(conductivity) −Log(water content) plot, supporting the TRC model concept. A unique relationship between the Campbell soil‐water …