This is the first investigation to report the processing and properties of ultrahigh molecular weight polyethylene (UHMWPE)/functionalized activated nanocarbon (FANC) gel solutions with the aid of supercritical carbon dioxide (scCO(2)). The ultradrawing and ultimate tensile properties of scCO(2)UHMWPE and scCO(2)UHMWPE/FANC fibers were found to improve considerably compared to those of UHMWPE and UHMWPE/FANC fibers prepared in the conventional way. The maximum achievable draw ratio obtained for the optimal scCO(2)UHMWPE/FANC fibers drawn at 95 degrees C reached 445. The highest tensile tenacity (sigma(f)) of the fully drawn scCO(2)UHMWPE/FANC fiber reached an extraordinary high value of 104 g/d, which is about 3.2 and 1.1 times of that of the optimal UHMWPE and UHMWPE/FANC fully drawn fibers, respectively. The sigma(f) obtained for the optimally fully drawn scCO(2)UHMWPE/FANC fiber is about 25 times of those of steel fibers and is the highest tensile tenacity ever reported for single-stage drawn polymeric fibers. Considerably lower dynamic transition temperatures and evaluated thinner crystal lamellae nucleated off of extended chains or FANC nucleants were found for as-prepared scCO(2)UHMWPE and scCO(2)UHMWPE/FANC fibers compared with UHMWPE and UHMWPE/FANC fibers, respectively. Specific surface area, morphological, and Fourier transform infrared analyses of the activated nanocarbon (ANC), acid-treated activated nanocarbon (ATANC) and FANC nanofillers and investigation of thermal, morphological, and orientation factor properties of the as-prepared and drawn UHMWPE, UHMWPE/FANC, scCO(2)UHMWPE, and scCO(2)UHMWPE/FANC fibers were performed to understand the remarkable ultradrawing, dynamic transition, and ultimate tensile properties obtained for scCO(2)UHMWPE and scCO(2)UHMWPE/FANC fibers. POLYM. ENG. SCI., 59:1462-1471 2019. (c) 2019 Society of Plastics Engineers