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The ignition delay times of gas-phase n-undecane/air mixtures in a heated shock tube were measured over a wide range of temperatures, from 731 to 1399 K, at pressures of approximately 2.02 × 10 5 and 10.10 × 10 5 Pa, and at equivalence ratios of 0.5, 1.0, and 2.0. This study represents the first-ever investigation of the shock tube ignition delay times of the n-undecane/air. The ignition delay times were determined by monitoring the reflected shock pressure and OH* emission at a location on the sidewall of the shock tube. The results show that the ignition delay time increases as the temperature is decreased above 910 K, then decreases with decreasing temperature between 910 and 780 K (thus exhibiting a negative temperature coefficient behavior), and finally increases again as the temperature is further reduced below 780 K. An increase in pressure was found to decrease the ignition delay time. The effect of the equivalence ratio on the ignition delay is different at the two experimental pressures, and the ignition delay is evidently highly sensitive to the equivalence ratio in the low temperature region compared with the high temperature region. The results obtained in this work are 2216 ZHANG Wei-Feng et al.: A Shock Tube Study of n-Undecane/Air Ignition Delays over a Wide Range of Temperatures No.9