<p>Efficient heat and mass transport in non-Newtonian nanofluids containing motile micro-organisms is important in advanced thermal systems, microfluidic devices, and biomedical transport processes. The present study investigates the combined effects of viscous dissipation, Joule heating, chemical reaction, heat generation or absorption, and bioconvection on magnetohydrodynamic (MHD) Williamson nanofluid flow over an inclined stretching surface. Brownian motion, thermophoresis, and micro-organism transport are incorporated to characterize the coupled thermal, solutal, and bioconvective mechanisms. The governing boundary layer equations are transformed into a system of nonlinear ordinary differential equations using similarity transformations and solved numerically with MATLAB’s bvp4c solver. The results indicate that increasing the magnetic parameter, Williamson parameter, and heat generation/absorption parameter suppresses fluid velocity, whereas a larger inclination angle enhances the velocity distribution. Higher Eckert and Brownian motion parameters increase the temperature field, while the temperature decreases with increasing inclination angle, thermal Grashof number, and solutal Grashof number. Nanoparticle concentration decreases with increasing Schmidt number and chemical reaction parameter, while the density of motile micro-organisms decreases with increasing Peclet number and bioconvective Lewis number. Furthermore, the Nusselt number decreases with increasing Eckert, Brownian motion, and thermophoresis parameters, whereas the Sherwood number increases with increasing Schmidt number, Brownian motion parameter, and thermophoresis parameter. The work gives important insights into the coupling of heat, mass and microbe transport processes in electrically conducting Williamson nanofluid systems for thermal engineering and biological applications.</p>