PVA and PVA/SWNT fibers (PVA = poly(vinyl alcohol), SWNT = single-walled nanotubes) were processed by gel spinning. At 1 wt.-% SWNT loading, tensile strength increased from 1.6 GPa for the control PVA to 2.6 GPa for PVA/SWNT composite. Analysis of this data suggests stress of up to ≈116 GPa on the SWNT in the composite fiber. This confirms excellent reinforcement and load transfer of SWNT in the PVA matrix. Tensile modulus of the fiber is also increased from 47 GPa for the control to 70 GPa for the composite. Interfacial studies using high-resolution transmission electron microscopy reveal extended-chain crystal growth of PVA at the PVA–SWNT interface. High SWNT alignment in the fiber is revealed, where the polarized Raman G-band ratio  is as high as 106. Composite fiber shrinkage in water is reduced by ∼70% when compared to the control PVA fibers.