Quebrada Lagunillas is an intermittent natural watercourse located in the Coquimbo Region of Chile, flowing from east to west across a stretch of approximately 28 kilometers before emptying into Laguna Adelaida on the shores of Bahía Guanaqueros. The stream originates west of the La Serena–Ovalle highway and west of the small settlement of El Peñón, forming at the confluence of Quebradas Martínez, Cortadera, and Las Cardas. From there, it cuts westward through the coastal mountain range in a deep gorge before reaching the lowland plains known as the Llanos de Lagunillas near Bahía de Guanaqueros. The watershed covers a drainage basin of approximately 512 square kilometers, making it a notable hydrological feature of this semi-arid coastal region of north-central Chile.