Energy efficiency issues in building lighting sectors often stem from human negligence in turning off electronic devices, resulting in significant operational electricity costs. This research aims to design and implement a smart light control system based on the Internet of Things (IoT) using the ESP8266 microcontroller, HC-SR501 PIR sensor, and Blynk platform. The method used is experimental with a hardware design approach separating low and high current paths, alongside software development using non-blocking logic in Arduino IDE. Integration with the IoT platform allows dual control: automation based on motion detection and remote manual control via mobile application. Test results show the PIR sensor has a 100% detection accuracy rate at an optimal distance of up to 4 meters. Furthermore, efficiency analysis shows that this system implementation can reduce unnecessary active lamp duration, resulting in an average energy saving of ± 45.8% compared to manual systems. This study concludes that the combination of physical sensors and cloud-based control is a reliable and responsive solution to support energy conservation in modern buildings.