The complete electroweak O(α) corrections are calculated for the charged-current four-fermion production processes e + e − → ν τ τ + µ −ν µ , udµ −ν µ , and udsc. The calculation is performed using complex gauge-boson masses, supplemented by complex couplings to restore gauge invariance. The evaluation of the occurring one-loop tensor integrals, which include 5-and 6-point functions, requires new techniques. Explicit numerical results are presented for total cross sections in the energy range from the W-pair-production threshold region up to a scattering energy of 2 TeV. A comparison with the predictions based on the "double-pole approximation" (DPA) provided by the generator RacoonWW reveals corrections beyond DPA of < ∼ 0.5% in the energy range 170−300 GeV, in agreement with previous estimates for the intrinsic DPA uncertainty. The difference to the DPA increases to 1−2% for √ s ∼ 1−2 TeV. At threshold, where the DPA becomes unreliable, the full O(α) calculation corrects an improved Born approximation (IBA) by about 1.6%, also consistent with an error estimate of the IBA.