This paper presents a capacitor-less low-dropout (OCL-LDO) regulator that features a low quiescent current for low power applications. To enhance the transient response of proposed OCL-LDO, a sub-threshold transient enhancement circuit including a transient signal input stage, a current subtractor, and a current amplifier is suggested. Meanwhile, a circuit made up of a bulk-driven ripple feed-forward circuit and a ripple introduction circuit is developed in order to improve PSR of the OCL-LDO. The proposed OCL-LDO is fabricated in 0.18 μm standard CMOS process and has an active area of 0.053 mm2. Based on measurement results, the proposed OCL-LDO has a maximum load current of 100 mA at 1.2 V input and 1 V output, and a minimum quiescent current of 0.91 μA. The overshoot voltage and undershoot voltage are 199 mV and 204 mV, respectively. PSR of the OCL-LDO is −71.8 dB at 1 KHz when the load current is 100 mA. Furthermore, the OCL-LDO exhibits a load regulation of 11.1 μV/mA and a line regulation of 1.05 mV/V.